We evaluate the effect of discussion on the accuracy of collaborative judgments. In contrast to prior research, we show that discussion can either aid or impede accuracy relative to simple averaging of collaborators’ independent judgments, as a systematic function of task type and interaction process. On estimation tasks with a wide range of potential estimates, discussion aided accuracy by helping participants prevent and eliminate egregious errors. On estimation tasks with a naturally bounded range, discussion following independent estimates performed on par with averaging. Importantly, if participants did not first make independent estimates, discussion significantly harmed accuracy by limiting the range of considered estimates, independent of task type. Our research shows that discussion can be a powerful tool for error reduction, but only when structured appropriately: Decision-makers should form independent judgments in order to consider a wide range of possible answers, and then use discussion to eliminate extremely large errors.