This paper reflects our ongoing interest in discovering essential elements of facilitation in decision support for groups with members having different perspectives on a strategic problem. We investigated questioning behaviour, a critical aspect of microlevel behaviour, of the facilitator in a classroom experiment with five-person groups (N 26). The supported groups used a facilitated modelling approach, that is, group model building, which is based on system dynamics. In the control condition, one of the participants led the group discussion in the role of chairperson. As expected, we found that the facilitator asked more questions than the chairperson. Subsequently, based on proposed functions of questions by discussion leaders in group decision making, we distinguished three categories of questions; related to (a) rational and social validation, (b) reflection, and (c) information management. Analysis of question type frequencies revealed that facilitators mainly ask questions from the rational and social validation category, and that this question type declines over the course of the discussion process. Questions prompting reflection increased over time. Information management questions were mostly used in the beginning and middle part of the session. In the groups led by a chairperson, a less clear picture emerged. There was a great variety between groups with respect to type of questions and sequence in which the chairperson asked questions. The only consistent result for unsupported meetings is that information management primarily took place at the end of the sessions.