This study focuses on the impact of the composition of groups of students on subjective psychological factors and the evaluation of collaborative work. The main results of collaborative work carried out by eighty undergraduate students show that the feelings of satisfaction and cohesion are different depending on the group composition. There is also a strong effect of affinity on peer evaluation and the accuracy of self-evaluation. It was also noted that some evaluation criteria for collaborative work are more interesting than others. Students are more likely to assess themselves more accurately when it comes to taking initiative regarding the amount of work done, or to an overall assessment of the work.