Abstract: This article explores the problems of Ukraine's integration into the European security system. Special attention is given to the questions of cooperation with the European Union, NATO and the OSCE that play an important role in promotion of security in the European continent. Emphasis is made on the analysis of the Ukrainian normative legal framework responsible for inclusion of Ukraine into the core structures of European security. Since 1991 to the present, all presidents of post-Soviet Ukraine from L. Kravchuk to V. Zelensky contributed considerably to the country’s integration into the European security system. With the development of relations with NATO, EU and OSCE, Ukraine sought to cooperate with the Eastern European countries within the framework of the key institutions of European security. Ukraine’s relations with certain Balkan states have experienced intense contradictions, for example dispute over the plan to liquidate Bolhradsky district in Odessa Region that was predominantly populated by ethnic Bulgarians. Since 2004, the territorial dispute between Ukraine and Romania pertaining to delimitation of continental shelf around the Snake Island has not been fully settled. The conflict between the two countries also aggravated due to the policy of reducing the Romanian-language educational establishments in Ukraine. Ukraine’s inclusion into the key structures of the European security is also impeded by Donbass armed conflict, the fact that the government of Ukraine does not recognize the Republic of Crimea's claim to sovereignty, as well as regularization of relations with the Russian Federation. The acquired results allow determining the motives underlying the foreign policy course of Ukraine that is aimed at its accession to the European Union and NATO, as well as the attempts to take its place within the European security system.