This study investigated the effects of collaboration mode and group composition during a computer-mediated collaborative (CMC) program. Six intact sections of a computer literacy course were assigned to either a face-to-face or a virtual, online collaboration treatment condition. Groups consisted of homogeneous lower-ability, homogeneous higher-ability, or heterogeneous-ability pairs. The study examined the effects of collaboration mode and group composition on individual posttest performance, group project performance, collaborative interaction behavior, and attitudes towards the instruction. Results indicated that virtual dyads exhibited significantly more questioning behaviors and significantly better project performance than those who collaborated face-to-face. By comparison, students in the face-to-face condition performed significantly better on the individual posttest than those in the virtual online condition. Findings suggest that both virtual and face-to-face collaboration can be effective in achieving learning goals. However, consideration should be given to the collaborative structure of the lesson and the type of task in the design of CMC environments.