Abstract: The rapid development of online health communities provides an important platform for patients to obtain health information and seek social support. However, users always acquire much knowledge from the platforms but lack the contribution intention, which will lead to the failure of online health communities. Based on the social capital theory, this research examined the factors affecting users’ participation. 312 valid samples were collected and analyzed with the LISREL software. It was found that social support, which includes informational support and emotional support, affects users' knowledge contribution and acquisition behavior through social capital. Thus, online health communities should pay attention to users’ informational and emotional needs and develop users’ social capital in order to promote the participation of members.

Key words: Online health communities, Social capital theory, Participation behaviour, User behavior, Knowledge access, Knowledge contribution, Trust