Social media, and specifically social networking sites (SNSs), are emerging as an important platform for communication and health information exchange. Yet, despite the increase in popularity and use, only a limited number of empirical studies document which segments of the adult population are and are not using social networking sites and with what, if any, affect on health. The purpose of this study is to identify potential communication inequalities in social networking site use among a representative sample of U.S. adults and to examine the association between SNS use and psychological well-being. We analyzed data from the National Cancer Institute's 2007 Health Information National Trends Survey (HINTS). Thirty-five percent of online adults reported SNS use within the past 12 months, and there were no significant differences in SNS use by race/ethnicity or socioeconomic position. Younger age (p = .00) was the most significant predictor of SNS use, while being married (p = .02) and having a history of cancer (p = .02) were associated with a decreased odds of SNS use. SNS use was significantly associated with a 0.80 (p = .00) increment in psychological distress score after controlling for other factors. The absence of inequalities in adult SNS use across race/ethnicity and class offers some support for the continued use of social media to promote public health efforts; however, issues such as the persisting digital divide and potential deleterious effects of SNS use on psychological well-being need to be addressed.