The presidency institution is of special importance to the majority of Post-Soviet States and plays a key role in their respective political arenas. At the same time, the existing institutional mechanisms of presidential power significantly differ from the "classic" world models which they were initially based on. This is true for the nature of the presidency institution and, to a greater degree, to the peculiarities of its function. Even though the institutional design of their political systems differs significantly, the presidential power in Post-Soviet countries functions in fairly similar ways. With that said, it appears necessary to identify patterns of development of the presidency institution in the Post-Soviet countries that developed over almost three decades. Pursuant thereto, this article attempts to analyze the dynamics of development of the presidency institution in these states, their respective peculiarities of function, the existing institutional mechanisms of interaction between the head of state and other public authorities, as well as its influence on the political system as a whole. The author looks at the presidential power not only from the formal-institutional perspective but also takes into account the most frequent informal practices.