The conformance and performance principles in territorial cooperation: a critical reflection on the evaluation of INTERREG projects. Regional Studies. In view of the influence that the diverse national and regional contexts of project partners has on the success of European Territorial Cooperation (ETC) projects, this article argues that a realistic evaluation of projects should consider not only the achievement of stated objectives (conformance) but also the range of dissemination activities and learning effects realized during the project (performance). Here a specific evaluation method is introduced that takes account both the conformance and the performance principles. Using the example of impact analysis of a transnational cooperation project and a cross-border cooperation project, it is shown that this evaluation method can contribute to a more suitable assessment of ETC projects.