Group Support Systems (GSS) have been the subject of much research over the past decade, but drawing overall conclusions about their effects has not been easy. In some studies, GSS use has improved performance, while in others, it has had no effects, or even resulted in decreased performance. This study presents a meta-analysis investigating the effects of GSS use in face-to-face decision making on effectiveness, efficiency, and participant satisfaction. The results suggest that, in general, GSS use improves decision quality, increases the number of ideas generated, requires more time to complete the task, and has no effect on participant satisfaction. However, the effects depend greatly on the size of the group and whether the process used by the group (solely electronic communication or a combination of electronic and verbal) matches the task (idea generation or decision making). Large groups benefitted significantly more from GSS use than small groups (for whom GSS use had few benefits). Groups for whom the process matched the task (electronic communication for idea generation and a combination of electronic and verbal for decision making) benefitted significantly more from GSS use (better decisions and more ideas) than groups for whom the process did not match.