This study is based on interviews with nine BSR regions that have been lead partners or partners in Interreg S3 projects: Central Finland, Hamburg, Helsinki-Uusimaa, Lithuania, Mecklenburg-Western Pomerania, Päijät-Häme, Tampere Region, Trøndelag and Västerbotten. The study describes their regional S3 process stories, good practices and interregional activities tested in various S3 Interreg projects. The insights and case studies developed in this study aim to support Baltic Sea regions in improving overall capacity across the Baltic Sea Region for strategic thematic collaboration.