AbstractWe introduce a systematic method to compare externalized mental models with a group model resulting from a group model building (GMB) process. To this end, we categorize the various concepts included in the models, and propose Venn diagrams and matrices to demonstrate the composition of the group model and identify the overlapping categories. We then suggest a set of metrics to analyze the matrices. We apply our method to a dataset of three GMB processes, finding the suggested method to be helpful for evaluating the extent to which all participants were able to include their perspectives, and whether new ideas emerged from the process, thus constituting innovation. We conclude that our method may be a valuable contribution to the evaluation of GMB processes. Furthermore, we demonstrate that the categorization of the concepts is a delicate process and has a significant influence on the results. Copyright © 2015 System Dynamics Society