This ethnographic study examines how participatory spaces and citizenship are co-constituted in participatory healthcare improvement efforts. We propose a theoretical framework for participatory citizenship in which acts of citizenship in healthcare are understood in terms of the spaces they are in. Participatory spaces consist of material, temporal and social dimensions that constrain citizens' actions. Participants draw on external resources to try to make participatory spaces more productive and collaborative, to connect and expand them. We identify three classes of tactics they use to do this: 'plotting', 'transient combination' and 'interconnecting'. All tactics help participants assemble to a greater or lesser extent a less fragmented participatory landscape with more potential for positive impact on healthcare. Participants' acts of citizenship both shape and are shaped by participatory spaces. To understand participatory citizenship, we should take spatiality into account, and track the ongoing spatial negotiations and productions through which people can improve healthcare.