The article presents proposed systematisation of international activity of regions (constituent parts of states) – regional paradiplomacy – within the framework of international relations studies. The author outlines the problems with defining the concept in question, the determinants of increasing activity of regions in international relations as well as the development of paradiplomacy studies. Furthermore, the author points out the dynamism and complexity of the analysed phenomenon as well as the vagueness of the concept of regional paradiplomacy and the need to conduct further studies on the issue.