Collaborative Virtual Environments provide new working methods to associate several users on the same problem through different space and time configurations (synchronous/ asynchronous, distant/colocated). This new approach enables the simultaneous management of complex environments with several constraints for a more robust and efficient process. Previous studies investigate various features of synchronous Collaborative Virtual Environment but they mainly focus on configurations involving mainly 2 users. This paper presents an experimental study which investigates the collaborative work for more users. We propose to compare 2 users with 4 users to perform a closely coupled molecular deformation task. The results show that groups of 4 participants are more efficient than pairs, even more if they plan their actions during a brainstorming step. An important outcome of this study shows that the role of a leader improve the coordination between the participants and limit the conflicting communication.