The article deals with the adaptation of Belorussian and Russian affixes in Polish dialects of Braslaw region. The author singles out certain models of af fixal adaptation on the basis of phonetic, morphological and semantic or phonomorphological equivalence. Collected vocabulary provides many examples where we can observe the assimilation of foreign elements into the native system of the multilingual population. Modifications of borrowings in this way indicate the vitality of the systemic word-formative rules of the Polish language in the speakers’ consciousness.