This paper systematises knowledge of public participation by bringing together existing concepts and theories from planning literature to conceptualise the 3A3-framework of participation. The framework presents participation as an emergent phenomenon, shaped by the dimensions: actors, arenas and aims. Each of these dimensions consists of three interacting elements. The framework highlights interdependencies between these elements and reflects them in the light of their embeddedness in planning processes and the wider social, cultural, political, spatial and temporal context. The framework can be used to gain a better understanding of what constitutes the phenomenon of participation. It enables the reflection of different forms of participation and contributes to more nuanced, and context-sensitive conceptions of and approaches to public participation in planning.