The number of public policy conflicts has increased sharply in most western democracies, especially in the fields of planning, regional development, and environmental policy. Attempts have been made to find a way out through new forms of negotiation-based conflict resolution. Alternative Dispute Resolution raises high expectations as to its potential for reaching consensual solutions, to be achieved through extended participation, transparency, and procedural justice. However, success or failure of negotiations do not depend only on the procedure, but also on factors exogenous to it. The first section addresses the question: which exogenous factors affect the opportunities for an agreement in public policy negotiations and how do they exert their influence? Spatial representation of bargaining is used as an analytical framework. The second section shows how outside options, exogenous restrictions, and political directives for the negotiators affected the negotiation space and the final outcome in a case of environmental mediation in Germany.