Smoking lapses during a cessation attempt are common and are thought to be a key predictor of full relapse. Positive and negative affective states have been hypothesized as important precipitants of lapses during quit attempts, although findings have been mixed. Accumulating evidence suggests that women may smoke more when experiencing negative affective states, while men may smoke more when experiencing positive affective states. The possibility that these sex differences may play a role in predicting lapses during a smoking cessation attempt, however, has not been well-investigated. In this study, we hypothesized that, during a quit attempt, negative affect would be more strongly associated with lapses among women, and positive affect would be more strongly associated with lapses among men.We conducted a prospective study in which male and female nicotine-dependent smokers (n = 60) made an unaided, ‘cold-turkey’ quit attempt. For fourteen days following the initiation of the quit attempt, participants completed daily diaries in which they recorded the degree to which states of ‘good mood’ and ‘bad mood’ preceded smoking lapses.Consistent with the study hypothesis, findings indicated that men reported higher good-mood-induced smoking lapses than women across the 14-day study interval. Conversely, while levels of bad-mood-induced smoking subsided over the 14-day interval among men, levels persisted among women.Results further underscore the need to address sex-specific affective triggers when developing smoking cessation strategies.