This paper presents research on the word-formation properties of onomatopoeia, or words imitating natural sounds. The research is conducted with the model of derivational networks, a relatively new approach to the theory of derivational paradigms, introduced for the first time in the book Derivational Networks Across Languages. The main aim of the analysis is to discover whether onomatopoeia can become a productive word-formation bases, and if so, how productive, and what kind of derivatives can be created. The research also compares English and Slovak onomatopoeia. The paper is divided into three main sections: part 2 introduces the concept of derivational networks and discusses its evolution through the works of Czech and Slovak linguists. Part 3 discusses the notion of onomatopoeia, what it is, and how it is understood and defined for the purpose of this research. Finally, part 4 presents the research itself, including the methodology, results, and discussion.