The article presents development stages of Baltic Europe cooperation in the political system after World War II based on the example of cross-border relations between Kaliningrad Oblast of the Russian Federation and Poland. After 1945 to the beginning of the nineties, the divisi on of the region into a well developed north western part and the south eastern part isolated from western countries determined the specific cross-border cooperation in this part of Europe. The article describes the various aspects and forms of cooperation, its spatial range and character, impact on local society and the significance for integration of Baltic Europe as a whole. The development of cross-border cooperation between Poland and the Kaliningrad Oblast may be divided into several stages. In the period 1945 to 1956 there were no forms of Polish Russian cross-border relations in place. The years 1956-1989 were a period of establishing and instigating at the beginning highly politically tinted relations governed by top down decisions of authorities in power. They specified the territorial range, the sectors and forms of cross-border contacts, restricting the number of participants and the frequency of trips abroad. Though so many restrictions limiting the first cross-border liaisons were present, the initial, predominantly institutional relations related to culture, education and sport were established. The beginnings of system transformations in the eighties and nineties in Central and Eastern Europe initiated a new stage in the development of cross-border cooperation, also in this part of Baltic Europe. Cooperation devoid of political aspects developed in many areas, e.g. in economy, tourism, cooperation of local authorities, environmental protection, transport infrastructure. Opening of borders for all citizens proliferated the border traffic earlier rationed and limited to official delegations. The situation also contributed to the development of interpersonal relations. An important event contributing to the development of cross-border cooperation was Poland's access to the European Union. Financial resources assigned to developing cooperation in the pre accession period as well as later provided significant support not only for development processes in the Polish Russian as well as Lithuanian and Polish relations. The accession of Poland to EU, and next to the Schengen Area, was related to the new regime for border crossings that hindered and diminished relations between neighbouring regions. A chance for revival appeared in 2012 in the poviats adjacent to the border in the Warmińsko- Mazurskie Voivodship and in the entire Kaliningrad Oblast with the introduction of small bordertraffic. This step led to activation of cross-border cooperation and consequently the local economy.