When the stakes of stakeholders are not properly incorporated during early phases of a planning process, it may later give rise to severe conflicts. The issue of how to deal with stakeholders in regional water management has been a subject of ongoing debate in the Netherlands. This paper promotes a 'platform' approach where stakeholders collectively attempt to develop plans for regional water management. Ideas for this platform approach are based on a review of research on groups governing common-pool resources. We argue that simple negotiation and mediation support tools can offer useful support and can serve to facilitate platform negotiations. We present a simple mediation and negotiation tool to support the early phases of such a land use planning process. The tool translates stakeholder preferences on the use of the landscape into spatially explicit value maps. Proposed plans can be evaluated and potential conflicts can be identified. The use of such a tool enables stakeholders and mediators to formulate explicitly the problems that need to be addressed in the decision-making process. © 2005 Elsevier B.V. All rights reserved.