If che is the workhorse of Italian relative clauses, cui is the indispensable specialist. Whenever a relative clause needs a preposition — the book I'm talking about, the person I wrote to, the city I live in — Italian abandons che and reaches for cui. This page covers all the standard prepositional uses, then the trickier possessive il/la/i/le cui that translates English whose.
Why cui exists
The reason Italian has two relative pronouns instead of one is purely syntactic. In English you can stack a preposition before which or whom (about which, to whom) or strand it at the end (the book I'm talking about). Italian doesn't allow either pattern with che — you can't say di che parlo, and you can't end a relative clause with a dangling preposition. So Italian invented a dedicated pronoun for these situations: cui.
Cui is invariable, like che. One form serves all genders, all numbers, all persons. The variability comes entirely from the preposition that precedes it.
Il libro di cui parlo è famoso.
The book I'm talking about is famous.
La persona a cui ho scritto è mia zia.
The person I wrote to is my aunt.
L'amico con cui esco stasera abita qui vicino.
The friend I'm going out with tonight lives nearby.
The common prepositional patterns
Here are the prepositions you'll meet most often before cui, with the structure of the resulting relative clause.
Di cui — about, of
Used for verbs and expressions that govern di: parlare di (to talk about), avere bisogno di (to need), fidarsi di (to trust), innamorarsi di (to fall in love with):
Il film di cui parlavamo ieri è uscito al cinema.
The film we were talking about yesterday came out at the cinema.
La cosa di cui ho più bisogno adesso è dormire.
The thing I need most right now is sleep.
L'amica di cui mi fido di più si chiama Anna.
The friend I trust most is called Anna.
A cui — to, at
Used after verbs and adjectives requiring a: scrivere a (to write to), pensare a (to think about), credere a (to believe), interessarsi a (to be interested in):
Il professore a cui ho scritto non mi ha ancora risposto.
The professor I wrote to hasn't answered me yet.
La cosa a cui penso più spesso è la mia famiglia.
The thing I think about most often is my family.
L'argomento a cui mi interesso è la storia romana.
The topic I'm interested in is Roman history.
Con cui — with
Used in the simplest sense of accompaniment, as well as instruments and means:
Le persone con cui lavoro sono molto gentili.
The people I work with are very kind.
La penna con cui scrivo è di mio nonno.
The pen I write with belonged to my grandfather.
L'auto con cui siamo venuti è in officina.
The car we came in is at the mechanic's.
In cui — in, into
Used for places, times, and abstract containers (situations, conditions):
L'epoca in cui viveva Dante è il Trecento.
The era in which Dante lived is the fourteenth century.
La città in cui sono nato è Bologna.
The city I was born in is Bologna.
Il giorno in cui ci siamo conosciuti era piovoso.
The day we met was rainy.
Per cui — for which, why
Frequently used to express purpose and reason. The phrase il motivo per cui is one of the most common collocations in Italian:
Il motivo per cui sono qui è semplice.
The reason I'm here is simple.
La ragione per cui ti chiamo è urgente.
The reason I'm calling you is urgent.
Lo scopo per cui studio è viaggiare in Italia.
The purpose for which I study is to travel in Italy.
Su cui — on, about
Used for surfaces, topics of writing, and subjects of focus:
Il tavolo su cui ho lasciato le chiavi è in cucina.
The table I left the keys on is in the kitchen.
L'argomento su cui sto scrivendo la tesi è complesso.
The topic I'm writing my thesis on is complex.
Da cui — from, by
For origin, agent in passive, or distance:
Il paese da cui vengo è in Toscana.
The town I come from is in Tuscany.
L'autore da cui è stato scritto il libro è famoso.
The author by whom the book was written is famous.
Tra cui / fra cui — among which, including
Useful in lists or to single out items from a group:
Ho letto molti romanzi, tra cui anche Il nome della rosa.
I've read many novels, including The Name of the Rose.
Sono venuti dieci amici, fra cui Marco e Luisa.
Ten friends came, among whom Marco and Luisa.
The possessive il/la/i/le cui — Italian's "whose"
This is where most learners stumble, because Italian's logic for whose runs in the opposite direction to English. Take a moment with this section — once it clicks, you'll have one of the most elegant constructions in the language.
The basic pattern
To say whose, Italian uses the article + cui + noun: il/la/i/le cui + noun. The article agrees with the noun that follows cui — that is, the thing being possessed — not with the antecedent (the possessor):
Lo scrittore il cui romanzo ha vinto il premio è italiano.
The writer whose novel won the prize is Italian.
Here the article il agrees with romanzo (masculine singular), even though the possessor — lo scrittore — is also masculine singular. The agreement is with the possessed noun.
La donna la cui figlia è attrice abita qui.
The woman whose daughter is an actress lives here.
The article la agrees with figlia (feminine singular), the daughter — not with la donna.
Le persone le cui idee mi piacciono sono pochissime.
The people whose ideas I like are very few.
Le agrees with idee (feminine plural). It happens to also be feminine plural to match le persone, but that's coincidence — the agreement rule looks at the noun after cui.
Why this works the opposite way from English
In English, whose points back to the possessor: the writer whose novel. The morphology of whose doesn't change with what follows. Italian's logic is genuinely the inverse — the article agrees forward with what is possessed, because grammatically that's the noun the article belongs to.
A useful mental rewrite: think of il cui romanzo as parallel to il suo romanzo (his novel). In il suo romanzo, the il agrees with romanzo. The same is true of il cui romanzo. Cui is replacing suo, not scrittore.
Examples across all four article forms
Il regista il cui film ha vinto a Cannes è giovane.
The director whose film won at Cannes is young.
L'attore la cui interpretazione è stata premiata è inglese.
The actor whose performance was awarded is English.
Lo studente i cui voti sono i migliori riceverà una borsa di studio.
The student whose grades are the best will receive a scholarship.
La cantante le cui canzoni amo di più è francese.
The singer whose songs I love most is French.
Notice that in the last three examples, the possessor and the possessed have different grammatical features — and the article tracks the possessed noun every time.
After a preposition: prep + il/la cui + noun
The possessive cui can also follow a preposition. The structure becomes [preposition] + [article] + cui + [noun]:
L'amico con la cui sorella esco si chiama Marco.
The friend whose sister I'm dating is called Marco.
Lo studente del cui lavoro ti ho parlato si è laureato.
The student whose work I told you about graduated.
These constructions sound formal and are more common in writing than in everyday speech, where speakers often restructure to avoid them.
Cui without article = "to whom" (older usage)
In older or literary Italian, cui without a preposition can mean to whom — a kind of fossilized indirect-object usage:
L'uomo cui devo tutto è mio padre.
The man to whom I owe everything is my father.
La persona cui rivolgo questa lettera è il direttore.
The person to whom I'm addressing this letter is the director.
This construction is grammatically equivalent to a cui (l'uomo a cui devo tutto) but feels more elevated. In contemporary speech, a cui is overwhelmingly preferred. Recognize the bare cui form when reading literature; in your own writing, use a cui.
The relationship to "il quale"
The fully formal alternative to cui is the inflected pronoun il quale / la quale / i quali / le quali, which behaves like an adjective and agrees in gender and number with the antecedent. The two are paraphrasable:
Il libro di cui parlo / Il libro del quale parlo.
The book I'm talking about.
L'amica a cui ho scritto / L'amica alla quale ho scritto.
The friend I wrote to.
In ordinary speech, cui is the standard choice — shorter, faster, no agreement to worry about. Use il quale when you need to disambiguate or when you're writing in a markedly formal register. See the il quale page for full coverage.
Cui in fixed expressions
A few high-frequency phrases live almost exclusively in their cui form:
Il motivo per cui ti chiedo è semplice.
The reason I'm asking is simple.
L'unica ragione per cui sono venuto è vederti.
The only reason I came is to see you.
In un certo senso, ecco il problema su cui dobbiamo lavorare.
In a sense, that's the problem we need to work on.
These collocations — il motivo per cui, la ragione per cui, il problema su cui — should be memorized as units.
Common Mistakes
1. Wrong article in the possessive construction
The most common error: agreeing the article with the antecedent (English logic) instead of with the noun after cui:
❌ Lo scrittore la cui romanzo ha vinto il premio.
Incorrect — 'romanzo' is masculine, so 'il cui' is required
✅ Lo scrittore il cui romanzo ha vinto il premio.
The writer whose novel won the prize.
❌ La donna il cui figlia è attrice.
Incorrect — 'figlia' is feminine, so 'la cui' is required
✅ La donna la cui figlia è attrice.
The woman whose daughter is an actress.
The fix is to ask: what gender and number is the noun immediately after cui? That's what the article must agree with.
2. Using che after a preposition
This error is so common it deserves to be flagged on every page that touches the relative system:
❌ Il film di che parlavamo ieri.
Incorrect — 'di che' is impossible
✅ Il film di cui parlavamo ieri.
The film we were talking about yesterday.
❌ La città in che vivo.
Incorrect — must be 'in cui' or 'nella quale'
✅ La città in cui vivo.
The city I live in.
3. Omitting the preposition before cui
English speakers sometimes leave out the preposition because in English you can strand or even drop it:
❌ Il libro cui parlo è famoso.
Incorrect — 'parlare' takes 'di', which must appear
✅ Il libro di cui parlo è famoso.
The book I'm talking about is famous.
❌ Le persone cui scrivo.
Incorrect (in modern Italian) — needs 'a cui'
✅ Le persone a cui scrivo.
The people I write to.
The preposition is dictated by the verb (or sometimes the noun). If parlare needs di, you say di cui. If scrivere needs a, you say a cui. Don't drop it.
4. Adding a redundant pronoun
Just as with che, you don't add a clitic pronoun for the role cui is already filling:
❌ Il libro di cui ne parlo.
Incorrect — 'ne' duplicates 'di cui'
✅ Il libro di cui parlo.
The book I'm talking about.
❌ La persona a cui le ho scritto.
Incorrect — 'le' duplicates 'a cui'
✅ La persona a cui ho scritto.
The person I wrote to.
5. Putting the article on the wrong side in possessive cui
A classic mistake is to attach the article to cui instead of placing it before:
❌ Lo scrittore cui il romanzo ha vinto il premio.
Incorrect — article goes BEFORE 'cui', not after
✅ Lo scrittore il cui romanzo ha vinto il premio.
The writer whose novel won the prize.
The structure is invariable: [il/la/i/le] + cui + [noun], in that order.
Quick reference
| Preposition | Construction | English |
|---|---|---|
| di | di cui | of/about which/whom |
| a | a cui | to which/whom |
| con | con cui | with which/whom |
| in | in cui | in which |
| per | per cui | for which/why |
| su | su cui | on which/about which |
| da | da cui | from/by which/whom |
| tra/fra | tra/fra cui | among which |
| (possessive) | il/la/i/le cui + noun | whose |
Key Takeaways
- Cui is invariable; it appears after a preposition or in the possessive il/la/i/le cui construction.
- The preposition is dictated by the verb. Memorize parlare di, scrivere a, credere a, fidarsi di.
- In il/la/i/le cui, the article agrees with the noun after cui (the thing possessed), not with the antecedent.
- Never use che after a preposition. Never repeat the role of cui with a clitic.
- For formal/literary alternatives, use del quale, al quale, etc. — see the il quale page.
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Open the Italian course →Related Topics
- Relative Pronoun Cui: With PrepositionsB1 — How to use cui — the invariable relative pronoun that follows every preposition in Italian, plus the distinctive il/la cui construction for 'whose'.
- Relative Clauses with CheA2 — How to use che — Italian's most versatile relative pronoun — to combine sentences and add information about people, things, and ideas.
- Relative Clauses with Il QualeB2 — How to use il quale, la quale, i quali, le quali — Italian's inflected, formal relative pronoun for clarity and elevated register.
- Subjunctive in Relative ClausesB2 — When relative clauses require the congiuntivo — the five core triggers and the logic that unifies them.
- Italian Prepositions: OverviewA1 — A map of the Italian preposition system — the nine simple prepositions, the obligatory contractions with the definite article, the prepositional phrases built on adverbs and nouns, and the lexical rule that towers over all of it: each verb and noun chooses its own preposition, and you must memorize them one by one.