Stable parties that successfully perform their representative function and connect to citizens are essential for democratic consolidation (Innes, 2002; Kreuzer & Pettai, 2004; Markowski, 2011; Tavits, 2013). Whether such parties will form in new European democracies has been questioned from early on (see Mair, 1997), but some degree of democratic stability has been achieved in the new East European EU member statesparticularly if we contrast them to most of the Former Soviet Union or Western Balkans. This chapter focuses on the development of political parties in countries that joined the EU in the first two waves; trends elsewhere in other post-communist countries differ considerably because of much lower levels of political stability or political freedoms. This chapter first looks at types of parties found in the region using a combination of two common approaches: party families and party development. The second section focusses in on the remarkably successful genuinely political parties without clear roots in the transition period and the related phenomenon of major parties suddenly becoming defunct. We then look at the internal life of parties through the analytical lens of party resources: symbiosis with the state, party organisations and membership. The conclusion summarises important trends since early 1990s and critically discusses the relationship between party development and democratic quality. PARTY TYPES Eastern Europe has been rich in the number and variety of political parties; to understand and analyse them, several approaches to party classification have been used. Party families is a classic and generally insightful approach that identifies similar parties across countries (Beyme, 1985; Hloušek & Kopeček, 2010). However, some parties defy easy classification, some families are internally diverse and parties can even change families. Also, it is not obvious why West European party families should provide a good guide to understanding parties elsewhere. Firstly, even if patterns of party competition in Eastern Europe have come to resemble Western Europe, a unique divisioncommunist legacyremains important in the former (Rohrschneider & Whitefield, 2013, p.84). Secondly, many East European parties have traits that are at odds with their reference "families" in the West (for a discussion on centre-right see Hanley, 2004); others are programmatically vague or flexiblenote the transformation of Fidesz from a liberal to a conservative party (Kiss, 2002). A related approach to classification is based on parties' membership in European party organisations. Yet, sometimes foes in national politics sit together and close allies in different party groups in the European Parliament. For example, as of 2016, the Czech, Estonian, Lithuanian and Slovak delegations to European People's Party or the Alliance of Liberals and Democrats included parties both from national government and opposition benches. Three broad groups of parties can be distinguished using a developmental approach: (a) former communists, (b) p...