To date, much research has been conducted on the positive and negative effects of online social networking (OSN). However, how users perceive others and themselves being subject to these effects and the consequences of users’ perceptions are understudied. Drawing from the third-person effect theory, this study examines the self-other perceptual gap for positive and negative effects of OSN and the consequences of perceptions for negative effects. Findings from our online survey (N=187) and interviews (N=8) suggested a significant difference between the perceived positive and negative effects on self and on others. Furthermore, the link between the third-person perception for usage risks of OSN and support for taking privacy protection actions was confirmed. We also found that the self–other discrepant perceptions were not influenced by age, time spent on OSN, number of OSN friends. However, gender emerged as a key difference in the third-person effects gap for privacy risks.