Does discussion in large groups help or hinder the wisdom of crowds? To give rise to the wisdom of crowds, by which large groups can yield surprisingly accurate answers, aggregation mechanisms such as averaging of opinions or majority voting rely on diversity of opinions, and independence between the voters. Discussion tends to reduce diversity and independence. On the other hand, discussion in small groups has been shown to improve the accuracy of individual answers. To test the effects of discussion in large groups, we gave groups of participants (N = 1958 participants in groups of size ranging from 22 to 212; mean 59) one of three types of problems (demonstrative, factual, ethical) to solve, first individually, and then through discussion. For demonstrative (logical or mathematical) problems, discussion improved individual answers, as well as the answer reached through aggregation. For factual problems, discussion improved individual answers, and either improved or had no effect on the answer reached through aggregation. Our results suggest that, for problems which have a correct answer, discussion in large groups does not detract from the effects of the wisdom of crowds, and tends on the contrary to improve on it.