Czy czyjaś osoba to osoba?

The aim of the article is to describe and explain the meaning of the Polish construction czyjaś osoba ‘the person of some person; persona’. The basis of investigations is the material culled out from the Polish corpora database (NKJP) and Polish historical and contemporary dictionaries. In the syntactic, as well as semantic analyses of the unit in question (esp. its syntactic function and collocations with predicates) the author reaches to a conclusion that: 1) the expression czyjaś osoba is semantic entity; 2) this unit can’t function as an agent in a sentence (persona/the person of some person isn’t someone or something); 3) the language unit czyjaś osoba isn’t equivalent of the notion of person.