Against the background of the increasing importance of evidence, knowledge and learning in both domestic and transnational policy development processes, this paper analyses how non-EU and intra-European Union knowledge arenas in spatial development policy and planning are connected by focussing specifically on the interrelationship between CEMAT and European Union activities and arenas of co-operation. The Council of Europe Conference of Ministers Responsible for Spatial/Regional Planning (CEMAT) has long served as a platform for pan-European (including both EU members and non-members) co-operation in spatial development, but has recently been sidelined by EU initiatives in this field of activity and even faced the possibility of discontinuation. Analysing potential areas of competition and complementarities/synergies and reviewing the recent Russian CEMAT Presidency, the paper argues that CEMAT retains an important role in connecting EU debates, practices and research with actors outside the European Union. However, institutionalised collaborative mechanisms and the systematic exchange of information between CEMAT and the EU in this field should be strengthened, particularly in a direction from EU to CEMAT and in the domain of research and evidence. Continuing with a sub-optimal level of co-operation between CEMAT and the EU in this field or even discontinuation of CEMAT would undoubtedly hamper the involvement and integration of non-EU members in the debate on European spatial development policy and would probably rather quickly lead to the significant disruption of the territorial knowledge channel linking the EU and Russia as well as that with the EU neighbourhood more broadly, while also significantly inhibiting the processes of learning on a pan-European level and stalling the development of a trajectory towards the emergence of something that would resemble a pan-European ‘epistemic community’ in spatial development policy and planning.