This article focuses on the development and “success” of the ex-communist parties in Eastern Europe and the former Soviet Union. It begins by testing the effects of several commonly cited variables that have been employed to explain the development and achievements of the ex-communist parties in post-communist politics. Second, it offers an alternative explanation that focuses on regime type, the presence of left-wing competitors, and the success of the ex-communist parties, and identifies three modal patterns of development: ex-communist parties that emerged from patrimonial communist systems (as in Russia and Bulgaria), ex-communist parties that emerged from national consensus systems (as in Hungary and Poland), and ex-communist parties that emerged from bureaucratic authoritarian systems (as in the Czech Republic). According to the author, ex-communist parties that evolved from national consensus regimes are more likely to survive the passage of time than those that emerged from other types of regimes.