The paper discusses a recent sociolinguistic study on the linguistic awareness of Polish youth from Lithuania, carried out in schools of the Polish national minority in Vilnius (Lithuania) in 2018. The study involves an analysis and comparison of responses about nationality, mother tongue, situational usage (interactive language use, non-interactive exposure, inner language) as well as knowledge of particular languages. Almost all Poles from Vilnius claim that they understand Russian, Lithuanian and Polish. The findings of the study are discussed in the context of the uniqueness of multilingualism and simultaneous usage of several languages. The research shows that the declaration of the mother tongue is a choice of identity in a multilingual society. At the end of school education, multilingual Poles are users of the Lithuanian language at the level of their native language.