The article examines the historical origins and further cooperation of the Lublin Triangle countries - Ukraine, Poland and Lithuania – Central and Eastern Europe, the history of which reflects the development of this region in the east of this part of the world. Combined by geographical proximity, foreign policy threats and a common socio-cultural tradition, they have a complex history of development and coexistence. The agreements made during a certain period of time are analyzed, conclusions are made. Opportunities have been identified for strengthening cooperation between the OSCE, the European Union, the Council of Europe, NATO and the Eastern Partnership countries. The possibility of joining the Republic of Belarus to a new format of relations and turning the triangle into a square for further joint cooperation in the direction of expanding opportunities in the field of energy, defense, cultural and social spheres was considered. The youth initiative on creation of a platform for interaction of youth of Ukraine with youth of Lithuania and Poland for the purpose of expansion of cultural, social and educational communications and an exchange of experience for creation of joint projects is considered. The future development of states and interstate initiatives depends on the active work of young people, the creation of the youth wing of the Lublin Triangle is a logical continuation of the interstate initiative, which will not only ensure youth participation in social and political life, but also positively affect Ukrainian-Polish-Lithuanian relations. thanks to youth diplomacy, will promote the development of European integration processes in Ukraine. An important initiative within the Lublin Triangle was the creation of a Lithuanian-Polish-Ukrainian brigade – LitPolUkrBrig, which provides for international peacekeeping and security operations under the auspices of the UN, EU, NATO and other international security organizations. Conclusions are made on the advantages and disadvantages of countries' participation in the new format of relations between the countries of the Lublin Triangle.