The article analyses lexical Lithuanisms in the Polish dialects of the Trakai region. The aim of this research was to show some aspects of archaic Lithuanian loanwords functioning such as: sphere of usage in certain semantic groups; their constant or occasional usage; their independent functioning or usage side by side with other languages borrowings. Up to now only a small group of widely spread words has been defined. As a rule, these are words which don't have any Polish eqiuivalent. They name people's physical appearance (kliszawy, lepaty, murzaty), their characteristic actions (kuciniac, rozkiereczyc sie), as well as plants (burkulki, lebiaki, jurginia), atmosphere phenomena (odliga, burbulki), etc. However, most Lithuanisms are used occasionally only in conversations about past life and old rural work (poszor, rezgini, plaskoni, szamocha, szylnik, skaracz). There is now doubt that these words occupied a certain place in the dialect in the past, while nowadays they are disappearing completely or are used equally with native Polish lexis or other languages adoptions, e.g. bronkt : orczyk; waga : brzozna; kudra : bizulka; szwilpiki : kakory. The article also analyses amorphous lexis and onomatopoeia functions in the Polish dialects of this region, e.g. szkir, juksz, put'-put'; gargac, krektac. .