This study analyzes the types of peer discussion that occur during lecture-based tutorial sessions. It focuses in particular on whether discussions of this kind have certain characteristics that might indicate success in the post-testing phase. The data were collected during an introductory physics course. The main data set was gathered with the aid of audio recordings. Data-driven content analysis was applied in the analysis to facilitate the placement of students’ discussions in particular categories related to different types of discussions. Four major discussion types were found: discussions related to the content knowledge, metalevel discussions including metaconceptual and metacognitive elements, discussions related to practical issues, and creating a base for discussion, seen here in the order of their prevalence. These categories were found to possess individual substructures that involved, for example, asking and answering questions, participating in a dialogue, or disagreeing with a peer. Analyzing the substructures of the categories revealed that there were evident differences between the groups, some of them related to the group size. With regard to the characteristics of discussions considered to be connected to a better learning outcome, it was observed that a great number of lines uttered related to the physics content or metalevel discussions seemed to have a direct bearing on success in the post test at the group level. For individual students, answering content-related questions posed by their peers might also indicate success in the post test. We would encourage researchers to continue this type of research in order to discover the essential characteristics of students’ discussions that facilitate learning.