The growing presence of the technology cause of an essential need to explore cancer patients’ behavior in online communities. Social Network Sites (SNS) such as Facebook provide an interactive environment to deliver health information to cancer patients. Only a few studies have looked at the role of Facebook for cancer patients despite their potential deliver health messages to large audiences. Hence, there should be more rigorous research to explain the cancer patients’ behavior in SNS. This study propose a theoretical framework to explore the cognitive, social and technological constructs that affect the performance of cancer patients in Facebook by using social cognitive theory (SCT). Based on purposive sampling, questionnaires were distributed to 178 breast cancer patients in cancer support groups in Peninsular Malaysia. Through this study, a basis for the investigation of Malaysian social network support in using SNSs is successfully established.