We compared the effects of text-, audio- and video-based communication methods on how people performed an appointment-scheduling task that involved both a cooperative and a conflict resolution component. The results showed that video-based communication method was more supportive of cooperative tasks when the task difficulty was high, and when there were more inherent conflicts in the task, in which more negotiation was required to resolve the conflicts. As a result, performance difference of the dyad was smaller in video communication. Different patterns of task completion time, problem space visitations and conversation dynamics further supported the effect of communication methods. Results of this study have important implications in understanding the process of collaborative problem solving and conflict resolution when different communication channels were used for remote collaborators.