While pre-electoral coalitions have important effects on the functioning of democracy, their formation has only been systematically examined in the context of established democracies. This study examines the patterns and factors of electoral alliance formation in eleven democracies in Central and Eastern Europe by focusing on joint candidate lists. It finds that electoral coalitions are more frequent in newer democracies than in established democracies. The formation of alliances is systematically related to their potential costs and benefits. On the one hand, coalitions can provide small parties with legislative representation and larger parties with important government coalition partners. On the other hand, parties face costs related to their electoral compatibility and the sharing of election candidacies and office positions.