OBJECTIVES This study aimed to identify the characteristics of social networking service (SNS) users and to assess the relationship of those factors to user satisfaction with the SNSs of the National Cancer Information Center (NCIC) in South Korea. METHODS A Web-based survey was completed by 1,670 users of the NCIC SNSs, who provided data on the sources they consulted for information about cancer, determinants of SNS use, sources of NCIC SNS awareness, the time of day they used the SNS, and their satisfaction level. RESULTS Facebook users mainly became aware of the NCIC SNSs through an acquaintance’s recommendation, while Twitter was accessed through other SNSs or blogs. Users in their 30s were less satisfied with the NCIC SNSs than those in their teens and 20s. Browsing for cancer-related information on the Internet, prioritizing information quality, and engaging in active use were related to a high level of satisfaction with the NCIC SNSs. Individuals who were exposed to the NCIC SNSs through other SNSs or printed materials were less satisfied with their experience of the NCIC SNSs than those who received a recommendation from an acquaintance. CONCLUSIONS These findings may act as a catalyst to guide public health agencies to enhance their use of SNSs.