Advertisements promoting and discouraging electronic nicotine products (ENPs) are widespread on social media. User interaction is a hallmark feature of social media sites. This study examined how user-comment valence (i.e. positive versus negative comments) influences attitudes toward counter-marketing ads, and determinants of ENP abstinence according to the theory of planned behavior (TPB). College students were randomly assigned to one of three conditions, a positive comment condition (n = 121), in which they were shown a YouTube comment section with eight positive comments and two negative comments; a negative comment condition (n = 126), in which they were shown a YouTube comment section with eight negative and two positive comments; and a control condition (n = 128). Then, all groups were shown a YouTube video advocating for ENP abstinence and completed measures about their attitudes toward the ad (Aad), attitudes toward ENP abstinence, injunctive and descriptive norms about ENP abstinence, perceived behavioral control (PBC) toward ENP abstinence, and intention to abstain from ENPs. Results indicated that exposure to negative comments yielded significantly less favorable Aad when compared to the positive condition, but no difference in Aad was observed between the negative and control conditions, or between the positive and control conditions. Further, there were no differences for any determinants of ENP abstinence. Additionally, Aad mediated the effects of negative comments on attitudes toward ENP abstinence, injunctive norms and descriptive norms about ENP abstinence, and behavioral intention. Findings indicate that negative user comments depress attitudes toward counter-persuasion ads targeting ENP use.