If citizens in the Netherlands do not agree with a decision of a public authority, they can submit a written objection. The Informal Pro-active Approach Model (or “informal approach”) provides an alternative for the traditional conflict resolution procedures. This informal approach has led to a reduction in the number of objections that resulted in a formal decision and in an increase in the number of objections that resulted in an agreement between the parties in the conflict. However, there is a growing need to be able to assess whether the informal approach is in fact successful. This paper focuses on the question what set of criteria should be used to assess the quality of procedures, the informal approach and their outcomes. It is important that the criteria reflect the purpose of the informal approach: to provide a fair procedure leading to an acceptable and legitimate outcome of the dispute between the citizen and the public authority. An assessment of four publications that formulate criteria relating to the course and outcomes of conflict resolution procedures and the analysis of the special features of the informal approach resulted in ten criteria that can be divided into three aspects: “Procedure”, “Outcome” and “Costs”. The “Procedure” aspect contains the criteria “interactive justice” (respect for individual/point of view, explanation about the procedure), “procedural justice” (in the narrow sense: equality of arms etc.), “usefulness of the mediating official” and “time”. The “Outcome” aspect contains the “satisfaction” with and “fairness” of the outcome, as experienced by citizens, and the (formal) outcome of the informal approach, as well as the legal quality of the outcome. The “Cost” aspect contains the criteria “financial costs” and “emotional costs”. In answering the question whether the informal approach is successful, discrepancies between the different aspects should be a point of departure for discussion about which aspects/elements of the informal approach need to be improved.