Two decades after the collapse of communism, there are major differences in the extent of democratization within the Iron Curtain countries. Aware of the complex mechanism to trace possible causes for such a variation, this study uses qualitative comparative analysis (QCA) to test the influence of nine international and domestic factors in influencing this process in 20 out of 29 post-communist countries. The evidence indicates that, out of all considered potential explanations, the perspective of the EU accession and a constant economic development are the primary propellers that induce democratization in the region. These quantitative results support and complement the literature that emphasizes the increased role played by the EU promise in the democratization process of the region.