The topic of this work is verbal prefixation , that is, the study of verbs with the same root but different prefixes. In this thesis, the purpose is to interpret verbal prefixes of related languages, but we will also talk about what functions and meanings verb prefixes can have when they encounter verbs. The related languages on the basis of which the research is carried out are Croatian and Slovenian, which we can say are languages in contact, and in addition, they also belong to the same language group, that is, to the South Slavic languages. The goal is to determine the similarities and differences between the meanings of verbs with the same roots but different prefixes, and in what measure is that problem the source of false friends. The assumption made is that non-equivalence in form also means non-equivalence in meaning. Verbs and their prefixes will be defined in the introduction, and then prefixes will be discussed in more detail. In addition, an answer will be given to the question of how Croatian and Slovenian grammars describe verbal prefixes, as well as prefixation itself, and what are the similarities and differences of prefixes in the mentioned languages. Likewise, related languages will be mentioned. In the same way, the term false friends will be defined, their typology listed, and the possible causes of their occurrence.The research part of the paper will present the results collected based on the conducted research on students of Slavic Studies at the Faculty of Philosophy of the University of Zagreb.