This paper describes a study on collective problem solving and decision-reaching in a CSCL (computer supported collaborative learning) environment. More specifically, the research is concerned with the influence of adding chat boxes and making explicit the roles of participants by icons on problem solving and decision performance. Groups of three persons had to solve two different tasks, an intellective problem solving and a decision-reaching task. In the control condition the groups simply communicated through the bulletin board, in the experimental condition the system is enhanced with chat boxes and role identification icons. Communication and performance on the tasks are considered as dependent variables. The results of experimental manipulations are presented and a discussion about how chat boxes and role indications influence construction of an accurate shared mental model used in problem solving and decision reaching is included.