The participation of the Catholic Church in the systemic changes in Poland is unquestionable. The significant role of church hierarchs, middle- and lower-level pastors in accelerating the erosion of the communist dictatorship in Poland over the years, and especially in the last decade of the Polish People’s Republic, is unquestionable. Analogous processes of political, social, economic and cultural changes taking place in neighboring countries where Catholicism was the dominant religion were also stimulated to a large extent by representatives of the clergy. However, the issue of the importance of the Orthodox Church in the Soviet Union for the systemic changes at the end of the 1980s remains slightly more complicated. Therefore, the article compares two powerful Churches, Catholic and Orthodox, from the point of view of analogy and diff erences in the role, influence and importance of these institutions for the collapse of both authoritarian systems.