Objective: This study examined dynamic effects of daily variations in craving and negative affect on the next-day risk of the first lapse and relapse among 149 adolescent daily smokers who achieved at least 24 hr of abstinence. Method: Participants completed real-time assessments of their smoking, craving, and negative affect 3 times per day during the 3 weeks after their quit attempt. The main outcome measures included the first lapse and relapse after at least 24 hr of abstinence from smoking. Results: Cox regression analyses with time-varying covariates showed that daily increases in craving predicted the risk of lapsing and relapsing on the following day, even after accounting for concurrent smoking and baseline levels of craving and nicotine dependence. Day-to-day variations in negative affect did not predict time to first lapse or relapse. Individual differences in baseline craving, nicotine dependence, and depressive symptoms also did not predict the first lapse or relapse. Conclusions: The findings challenge the significance of adolescents' negative affect during cessation and emphasize the need to assess dynamic effects of craving in addition to baseline ratings of craving and nicotine dependence, as the latter may not be sufficient to explain adolescent smoking cessation outcomes.