How can we explain the decline of parties while in opposition in Central and Eastern Europe? To answer this question, we first verified whether all of the parties spending more than two parliamentary terms in opposition in this region are declining. We then examined the factors that might explain this phenomenon. We chose to address two dimensions: an external dimension (contextual factors), and an internal dimension (organizational factors). For the former, we took into account the development of party systems during the transition period, while for the latter, we analyzed the splits that occurred while the parties were in opposition.