Using ambulatory methods for monitoring, this study investigated gender differences regarding the association between smoking and situational cues in 63 smokers with posttraumatic stress disorder (PTSD) and 32 smokers without PTSD. Smokers were instructed to complete a diary entry each time an ambulatory blood pressure monitor took a reading and each time they prepared to smoke. Generalized estimating equations contrasted 682 smoking and 444 nonsmoking situations by group status. For all smokers, ad lib smoking was strongly related to craving. For women with PTSD, ad lib smoking was strongly related to total PTSD symptoms, PTSD reexperiencing symptoms, and PTSD hyperarousal symptoms. For men with PTSD, ad lib smoking was significantly related to negative affect, PTSD reexperiencing symptoms, restlessness, and worry. No other mood antecedents were significant for women or men smokers without PTSD. These results are consistent with previous studies documenting gender differences in smoking behavior, and underscore the importance of examining gender differences in psychiatric samples.