Presented thesis Programs of the European Union of supporting regional interparliamentary cooperation in the region of Western Balkans as an instrument of regionalisation is focusing on regional parliamentary cooperation in the region of Western Balkans and programs of the European Union which are programmed to support this particular cooperation. The study is framed in the theory of new regionalism and the approach of socialization in international relations, which both offer in the case of European integration explanation of why regionalization takes place. The aim of the thesis is to answer the question whether the European Union is successful in its support of regionalization via regional parliamentary cooperation. Meaning if the mechanism of socialization chosen by the Union is effective and if institutional capacities of the national parliament in the region to conclude this cooperation are being built either via direct engagement with the Union, or via indirect way by engaging with regional initiatives active in regional parliamentary cooperation such as Regional Cooperation Council, COSAP and Cetinje Parliamentary Forum. By analyzing the mechanism of socialization and the environment in which the socialization takes place the thesis identifies if, and how much is the European Union able to...