This research compared social networking site (SNS) use in a collectivistic culture, China, and an individualistic culture, the United States (US). Over 400 college student participants from a Southwestern University in Chongqing, China, and 490 college participants from a Midwestern University in the US completed a survey about their use of SNSs – time spent, importance and motives for use. They then rated themselves on a variety of personal characteristics, namely the Big Five Personality factors, Loneliness, Shyness and Life Satisfaction. Results revealed cultural differences in SNS use. US participants spent more time in SNS, considered them to be more important and had more friends in SNSs than did Chinese participants. Self-ratings of personal characteristics also differed in the two cultures as did the personal characteristics that predicted SNS use. In general, personal characteristics were less effective in predicting SNS use in China than in the US. Findings suggest that in collectivistic cultures the importance of the family, friends and one’s groups may be partly responsible for Chinese participants’ lesser use of SNSs, whereas in individualistic cultures the importance of self and having more but less close and enduring friendships may be partly responsible for US participants’ greater use of SNSs. Personal characteristics predicted SNS use in both cultures but were stronger predictors in an individualistic culture than in a collectivistic, consistent with the emphasis on self in the former and on family, friends and one’s groups in the latter. Future research is needed to identify whether cultural values always take precedence over personal characteristics and motives in determining behavior in the virtual world.