The paper presents a dialogue method called Decision Structuring Dialogue to be used in group decision making. Through a focus on the facilitation of dialogue and on the conversational aspects of problem structuring, we show how Decision Structuring Dialogue facilitates collective framing and structuring of complex problems under conflicting interests. Decision Structuring Dialogue is suitable for structuring problems that involve multiple actors, multiple perspectives and conflicting interests. Decision Structuring Dialogue is a process helping to create a shared vision of the problem and the possible decision alternatives. It complements other problem structuring methods and acts as the first step in multiple criteria decision analysis. The method was successfully applied in the steering group of a Finnish lake regulation project with a high conflict factor.