This article focuses on the Central and Eastern European in the process of shaping their security relations. The aim of the paper is to present and analyze the evolution of security relations in the region under the aegis of the EU, NATO and the Organization for Security and Co-operation in Europe (OSCE). The interplay of the institutions shows that the EU is not a single power in the European security system thus the maintenance of stable and peaceful relations depend mostly on cooperation between a number of institutions and groupings. The EU and NATO’ s role was central due to their policies of enlargement and the stabilization effects on third partner countries. The OSCE with its well promising position in Europe has been weaken due to decline of interests of major power states and its functions performed simultaneously by the EU and NATO. Both organizations have taken to a large extent the place of the OSCE.