Science diplomacy (SD) is an emerging field of study at the intersection of international relations and science policy. Despite such a growing interest, the region of Central, Eastern and South-Eastern Europe has received limited attention by the scholars studying this increasingly significant topic. This article presents the preliminary results of a research focusing on international scientific collaborations between the countries that are members of the Central European Initiative (CEI), an intergovernmental forum for regional cooperation spanning across this broad region of Europe. Using social network analysis (SNA), the paper explores which countries are the most prominent in these cooperation networks and whether the countries sharing EU membership are clustered into separate, distinct subgroups, with fewer or weaker ties with Non-EU members.