This thesis generally deals with the process of démocratisation in post-communist Eastern Europe. Specifically, it explores the latter stages of this process: the consolidation and persistence of democracy, following the demise of the ancien regime and the conclusion of democratic transition. In other words, it tries to describe the conditions for and consequences of increased regime stability and legitimacy after the actual establishment of democracy. In theory, this usually happens after the initial holding of free and fair elections and the fulfilment of some other minimal criteria of political democracy like the existence of a multiparty system, the protection of the freedom of speech and the pluralism of media, the adoption of the constitution and the foundation of the basic political institutions of a democratic state. In practice, the consolidation of democracy is a never-ending process and even long-established democracies periodically face the problems of deconsolidation and reorganisation of their internal structure. This research, which began in the second half of the 1990s, has followed the majority of these scientific trends quite closely and has taken over some of the theoretical ideas, conceptual tools and research methods of the previous analytical explorations of Eastern Europe and other regions of the world. It has become progressively integrated within the mainstream comparative démocratisation studies, which was, and continues to be, the predominant research current focusing on democratic transition and consolidation. At the same, this thesis has acquired certain independent normative features and tried to comprehensively describe the conditions for consolidation of democracy in a post-communist context. The critical analysis of most of the recent theories of démocratisation has proceeded by testing several alternative hypotheses regarding the future of democracy in the region. Moreover, the normative research on the establishment of political democracy in Eastern Europe has been supplemented with an original method of conceptualising and measuring the degree of consolidation and the quality of democracy. Together with the extensive theoretical analysis of the different paths towards démocratisation, the final empirical section, featuring the innovative statistical Index o f Démocratisation (IDEM), are the two most significant contributions of this thesis.