Introduction According to Samuel P. Huntington great historical line that has existed for centuries separating Western Christian peoples from Muslim and Orthodox peoples runs along what are now borders between the Baltic states (Estonia, Latvia, Lithuania) and Russia [...] (Huntington 1998: 158). Estonia's geopolitical location on the border of two civilizations and its recent history, i.e. its turning from a small brother in the Soviet family into a sovereign subject of international law, or in other words, into an equal neighbour of the Russian Federation, make it an interesting subject for studying the driving forces and mechanisms of the emergence and maintenance of cooperation between the two countries differing substantially by size, importance on the international arena and cultural background. 10 years after the disintegration of the Soviet Union and peaceful restoration of Estonia's independence in 1991, between the two neighbours--Russian Federation with its population of approximately 150 million and Estonia with its population of only 1.4 million--still have considerable room for improvement. It has often been pointed out that cooperation between the two states has not been developing so well and quickly as desirable. In spite of declarations that dynamic and friendly with Russia are among Estonia's security policy priorities (Klaar 1997:18), the list of unresolved political, economic and social issues, hampering normal development of two neighbours, has not significantly shortened over the last decade. Despite long-lasting negotiations and assurances from both sides that technical questions have been solved, the two countries still have not succeeded in signing an official agreement on borders. Economic between the two states are often overshadowed by political considerations, e.g. the unfavourable taxation regime, imposed by Russian authorities on many of Estonian products. The legacy left by the Soviet military presence can also be considered as a source of tension--there were 1565 military objects of the former Soviet Union in Estonia with the total area in their possession of about 87.000 hectares, i.e. 1.9% of Estonia's territory. Damage to the environment was estimated at about 4 billion USD (Raukas 1999:119). Although not directly threatened by its eastern neighbour today, Russia is still often implicitly considered as one of the main outside threats to Estonian security (Vares 1999, Kivi 1999, Luha 1999). Hostility and threats from the Russian side have also several times been openly demonstrated (Kadak 1999:70). The Russian Federation, on the other hand, has been continuously expressing its discontent with several political priorities and developments in Estonia during the 1990s. A difficult and interrelated set of bilateral issues, and especially the inter-ethnic between Russian minority and Estonian majority has been the most outstanding bilateral problem from the Russian point of view (Russia and... 1998). One of Estonian political priorities--accession to NATO, has continuously been causing mistrust and misunderstanding between two neighbours (Loshchinin 1997: 13-14, Shustov 1998:18, Suslov 1999). In the frame of these unfavourable conditions, however, regular environmental cooperation between Estonia and the Russian Federation has emerged and is still being successfully maintained. Several intergovernmental agreements on fisheries and environmental protection have been negotiated and signed, regular meetings of intergovernmental bodies held, and in the field of environmental protection, both on governmental and on non-governmental levels, built and strengthened. International regimes--defined as sets of implicit or explicit principles, norms, rules and decision-making procedures around which actor's expectations converge in a given issue-area of international relations (Krasner 1983:2)--have been in the centre of scientific efforts to explain the emergence and maintenance of cooperative behaviour of state actors in the field of environmental protection (Zurn 1998). …