College student smokers (N = 50) were asked to carry electronic diaries for 14 days and record smoking events (n = 1,139). They indicated why they were smoking each cigarette on a checklist of potential motives. Results suggest that a desire to reduce craving (62.8% of occasions) and habit/automatic processes (42.8%) were the most frequent motives. More dependent and daily smokers were especially likely to endorse smoking to reduce craving and for habit/automatic reasons and were less likely to cite coping with negative emotion as a reason for smoking. Dependent and daily smokers were more likely to endorse at least 1 dependence-like motive and were less likely to exclusively attribute smoking to nondependence motives. Self-monitored motives appeared valid, according with conceptually related states, activities, and events in the diary records. Diary-recorded motives were compared with smokers' responses to a retrospective motives questionnaire administered at baseline. The 2 assessment modes produced discrepant estimates of the most influential motivational processes. Questionnaire responses incompletely forecast conceptually similar diary-reported motives. Dependence and daily smoking showed a different pattern of associations with diary-based versus retrospective motives measures.