This article documents and provides possible explanations for the degree of judicial activism in eight post-communist countries. We examined constitutional court cases for the three years following the initial adoption of a constitution in the Czech Republic, Estonia, Georgia, Latvia, Lithuania, Moldova, Russia, and Slovakia. We found that contextual political factors, such as the extent to which the party system is fragmented and the extent to which the court enjoys popular trust and confidence (rather than the formal powers entrusted to the court by the constitution or the structure of the political system), contribute most to the degree of activism by constitutional courts.