The thesis seek to understand the implications of the perspective of European integration on the mobilization of ethnic minorities and to answer the following question: to what extent and in which ways European integration shapes the mobilization of ethnic minorities in the newly democratic states of post-communist East Central Europe? To this end, a theoretical overview of the theories of European integration is provided and an analytical framework is built on various rational choice and social movement literature. Two independent variables (Homogeneity and convergence with European Union's policies and expectations) are identified to influence the type of mobilization that will prevail. Three hypothesis are being investigated: a homogeneous country that is EU convergent will have high political mobilization and low non-political mobilization; a country who is heterogeneous and not EU convergent will have a high level of non-political mobilization and low political mobilization; finally, a country that is heterogeneous and is EU convergent will have an even level of both types of mobilization. The analysis is based on three case studies that each represent a hypothesis: Hungary (Homogeneous and EU convergent), Romania (Heterogeneous and not EU convergent) and Latvia (Heterogeneous and EU convergent). The analysis reveals that the political opportunity structure is influenced by the presence of the EU which is considered as a soft veto player and confirms the hypotheses