Public participation is increasingly involved in collective decision-making processes at the local level, although what actually is meant by participation is rarely specified and varies widely. In Europe, the Water Framework Directive contains a specific article regarding participation. In Africa, new national policies have attempted to involve stakeholders and citizens in collective decision-making processes and in the implementation of their outputs. Participation is currently promoted by international institutions. This has led to the widespread acknowledgement that concerned people should be more involved in decision-making processes, at least in the field of natural resource management. This new trend towards participation is generating new issues: How should the involvement of stakeholders be implemented? What pitfalls need to be avoided and what side effects need to be managed? What can be considered as involvement of concerned people, and how diverse can such involvement be? Agent-based models (ABMs) and role playing games (RPGs) are increasingly being used, separately or together, to facilitate dialogue in territory planning and natural resource management (Bousquet et al, 2002). This is due to the capacity of such tools to simulate and handle complexity. This paper introduces such a tool, PIEPLUE, as a support for dialogue on water sharing issues. Before presenting PIEPLUE, we discuss some of the diversity in what is considered participation according to two dimensions: the level of involvement and the stage of involvement in the decision-making process. We also identify the pitfalls that PIEPLUE aims to circumvent, such as a disproportionate focus on private interests, the emergence of new lead groups which might not be legitimate and interference in existing conflicts.