BACKGROUND Smokers with posttraumatic stress disorder (PTSD) tend to lapse more quickly following a quit attempt, which might be explained by changes in PTSD symptoms during a quit attempt. The present study examines changes in PTSD symptoms, negative affect, and craving before and during a quit attempt. METHODS Participants in this study were 52 smokers with PTSD who completed random-alarm ecological momentary assessments of PTSD symptoms, negative affect, cigarette craving, and smoking behavior throughout a prequit phase of ad hoc smoking, a phase of abstinence from smoking, and a postlapse phase. RESULTS Relative to the prequit phase, the abstinent phase was marked by decreases in PTSD reexperiencing, avoidance, and numbing clusters (ps ≤ .01). The odds of PTSD symptom or negative affect variability from one reading in the ecological momentary assessment (EMA)to the next reading was decreased in PTSD reexperiencing, avoidance, and numbing clusters (ps ≤ .02). Smoking cravings were also mildly decreased in the abstinent and postlapse phases (ps < .01), although some cravings in both phases were rated at the maximum intensity. Increased craving was predicted by the previous EMA reading of PTSD symptoms. CONCLUSIONS Results suggested that smoking abstinence is not associated with exacerbation of PTSD symptoms, but PTSD symptoms during abstinence were related to craving levels during the quit attempt.