This study examined the effects of on-line group discussion on accuracy and confidence in solving reasoning problems, while also examining the effects of the accuracy and the confidence of group members before the discussion on the accuracy and change of answer following the discussion. The study involved 108 psychology students from the University of Rijeka, grouped into 36 on-line triads. Participants initially solved eight reasoning tasks, judging the confidence in their answers, followed by the group discussion of those tasks aimed at agreeing on the correct answer. They finished the study by providing their final answers and confidence judgements afterwards. Following the discussion, their accuracy improved in five tasks and their confidence increased in all eight tasks. Accuracy of the answer following the group discussion was not predicted by confidence judgements, but the initial accuracy of both the participant and other group members proved to be significant predictors. More initially correct answers were given withing a group, more likely it was for each single participant to answer correctly after the discussion. Participant’s correct initial answer and higher confidence decreased the probability of her changing her answer after the group discussion, while the higher confidence of other group member in another answer increase the probability of persuading the change of answer. These findings support the Argumentative theory of reason while demonstrating comparable effect of of-on line discussions on accuracy and confidence judgements of reasoning problems as live discussions.