In this article we propose a framework which can assist analysts in their reflection on the requirements for a participatory modelling exercise in natural resource management. Firstly, we distinguish different types of formal models which may be developed, ranging from models that focus on (bio)physical mechanisms to models which also include the actors involved in the utilisation of the resource and the social mechanisms that co-determine actor behaviour. Secondly, we consider what different modes of stakeholder participation entail for model construction and use. Finally, we propose six different purposes for a modelling exercise (clarify arguments and values, research and analyse, design and recommend, provide strategic advice, mediate, and democratise), and highlight conditions that affect the appropriateness of stakeholder participation for each purpose. The framework does not provide a straightforward recipe for the selection of participatory modelling methods, but we expect that the systematic reflection it affords will help analysts to make appropriate choices while designing a modelling exercise.