This study was driven by three underlying motivations. One of them is the gap between high penetration rate of mobile phone and relatively low adoption rate of m-commerce. The second is to reconcile the inconsistent findings in prior IT adoption research regarding the consistency of the relationship between attitude and intention. Finally, we hope to provide the theoretical underpinning for various interventions to promote m-commerce adoption. In this study, we extended the theory of planned behavior (TPB) by integrating confidence as a moderator for the relationship between attitude and intention. Furthermore, trial, communication and observation are identified as the sources for confidence with m-commerce and their effects are mediated through exposure. The research model was empirically tested and supported. Both theoretical and practical implications are discussed.