QuitNet is one of the most popular websites providing tools and services to help people quit smoking. QuitNet developed forums on its original website to help its users interact with each other. It also built a public page on Facebook, which provides another community for people to discuss issues of smoking cessation. This study compares user behaviors between the two communication channels on smoking cessation – QuitNet Forum and QuitNet Facebook. Social network analysis and user response immediacy were used to analyze user behavior on the two channels. It was found that users of QuitNet Forum participated in discussions more actively, while QuitNet Facebook users behaved more differently from each other.