Proficiency elements of criminal activity of mercenaries are inextricably linked to the comparative study regarding various criminal legislation, especially those which have common elements with national criminal law. Given the historical context of criminal law common development of countries of the Commonwealth of Independent States (CIS), in this article we deal with a comparative analysis aimed at legislation which concerns the offense of mercenary activity. Such an objective is natural, since comparative criminal law is an area of science of criminal law, which is intended to study rules and legal institutions belonging to different national systems in order to know the meaning and content, and the differences between these rules and institutions.