The article deals with the formation of political systems in states, which have emerged in Eastern Europe after the Cold War. It emphasises that the majority of states in the region made a choice in favour of presidential republics. The author have arrived at the conclusion that characterization of institute of presidentialism in a state under consideration as ‘authoritarian’, ‘hybrid’ or ‘democratic’ to a great extent depends on two factors: scope of constitutional authority of a president as well as practice of interpretation of this authority in concrete actions in political domain. Both factors could be under the influence of multiple processes, which include nature of the mutual interaction of institute of presidential power with three traditional branches of power in a sovereign state; a practice of relationship with civil society structures, business communities and media; historical experience and its interpretation in the concrete historical scenery. Last but not least nature of the political regime in a state and place of an institute of presidential power in it could be defined by personality of a politician, who hold the office of president, his or her education, political experience, communication skills, ability to communicate with representatives of other institutions of state power.