The concept of participation has become increasingly important in a range of institutions and disciplinary contexts. The different institutional and disciplinary fields often interact indirectly by building on the same or interconnected ideals, logics and discourses or by using the same or similar theories. But it is quite rare that spaces enabling interaction and learning about cross-institutional and cross-disciplinary participation are created. This special issue is an attempt to do just that, and thus also to stress the importance of such transdisciplinary ‘spaces’ of learning and knowledge. By facilitating such transdisciplinary spaces this issue strives to: show how various disciplines understand, use and design ‘participation’; learn from already established insights and faults; potentially develop common understandings of what participation is; understand how ideal and processes of participation are linked to structures of power; and create better tools or models to explore, valuate and create participatory values, qualities and effects among researchers and practitioners. The articles in the issue are dealing with participatory processes in healthcare, political NGOs online, the cultural sector, education, employment and urban design.