The contribution of media in fostering communications and exchanges of idea is an enduring topic of investigation. However, our review of existing theories on media and human cognition suggests that there remain taunting contradictions in their theoretical assumptions and postulations with regard to computer-mediated communication (CMC) usage. Specifically, the social presence theory postulates that a rich medium could better facilitate the communication activity by promoting a greater “awareness” of the communicating party, which may then lead to better task performance. Yet, a richer medium could also distract an individual's focus of attention as suggested by the cognitive theory of distraction-conflict. To reconcile these contradicting perspectives, this study conducted an empirical comparison of two CMC tools, i.e., Second Life and online chatroom, in terms of users' perceptions of the media and their actual task performance in these media. The results suggest that a rich medium, such as Second Life, could lead to better perceptual evaluations of users in terms of telepresence, curiosity arousal, and immersion in media. However, the use of a lean medium, such as chatroom, could lead to better task performance in terms of users' recall ability, and the quality of ideas generated during the mediated interactions. Implications for research and practice are discussed.