This paper deals with the semantic roles of nouns that end in –er in English and in –ač in Croatian. Both suffixes are productive in their respective languages. The goal of the research was to see which semantic roles can be taken by words formed with each of these suffixes. With the help of a theoretical overview and a research conducted in the corpora of English and Croatian, it was discovered that the suffix –er is much more polysemous than the suffix –ač, since it is productive in the formation of the majority of semantic roles in varying degrees. The suffix –ač is only productive in the formation of agent and instrument nouns. The suffix –er also attaches to a greater variety of bases than the suffix –ač. What can also be seen from the results of the research is that single English words with the suffix –er can more commonly take different semantic roles in context than the Croatian ones with the suffix –ač.