Internet-based virtual communities are growing with an unprecedented rate. Virtual communities have been viewed as platforms for sharing knowledge. The present study proposed an integrated model by investigating social capital and motivational factors that would influence the knowledge sharing attitude of members. Data were collected from 207 professional virtual community users (including 53 contributors and 154 lurkers). The results showed that trust and pro-sharing norms mediate the relationship between shared understanding and knowledge sharing attitude. Enjoy helping, commitment, and community-related outcome expectations enhance contributors’ attitudes toward knowledge sharing. When lurkers perceived more reciprocity in their communities and expect more community-related outcome, they incline to sharing knowledge with others. The implications of these results are discussed
