EN
The aim of this paper is to discuss the most common errors made by Ukrainian- and Russian-speaking students learning Polish as a foreign language as well as their causes. Slavic languages, despite numerous similarities, differ considerably. A command of one language from a given language group makes it easier to learn another one from the same group. However, knowledge of one Slavic language could also hamper the process of learning. The major causes of errors are considered to be interlanguage homonymy and the infl uence of negative interference. Incorrect pronunciation, in turn, causes problems with writing, that is spelling mistakes. People who know other Slavic languages often use words non-existent in Polish. A large number of the errors are syntactic ones.