The goal of this K23 Mentored Patient-Oriented Research Career Development Award is to broaden the candidate's expertise in smoking and psychiatric comorbidity research, particularly as it relates to Attention-Deficit/Hyperactivity Disorder (ADHD). Individuals with ADHD smoke cigarettes at a higher rate, initiate smoking at an earlier age, and have greater difficulty quitting compared to those without ADHD. Despite ADHD being a risk factor for such smoking outcomes, the mechanisms underlying this comorbidity are poorly understood. Delineating the role of these mechanisms is important for targeted treatment development. Emotion dysregulation is hypothesized to be a key behavioral mechanism that maintains cigarette smoking in ADHD smokers. Specifically, emotion dysregulation may worsen following smoking abstinence and make smoking more negatively reinforcing among smokers with ADHD, but this has yet to be empirically investigated. Training objectives will include gaining expertise in behavioral and psychopharmacological methods to measure behavioral mechanisms in smoking and ADHD, measuring emotion dysregulation in substance use and comorbid psychopathology research, bidirectional translation for future research building on laboratory-based findings, and statistical proficiency in clinical research. These objectives will be met through mentoring, research, and coursework, which will result in an independently funded program of research to (1) elucidate underlying behavioral mechanisms, including emotion dysregulation, involved in comorbid smoking psychiatric populations such as ADHD and (2) develop innovative cigarette smoking treatment for comorbid psychiatric populations. Dr. Scott Kollins, the primary mentor for this application, has a strong record of clinical research assessing the relationship between cigarette smoking and ADHD. He is also the director of the established research training site where the applicant will be trained. The research plan involves evaluating the association between cigarette smoking and emotion dysregulation in a mixed 2 (group status: ADHD, non- ADHD smokers) x 2 (smoking status: satiated, abstinent) factorial design. The primary hypothesis predicts that emotion dysregulation is more likely to worsen following a period of 24-hour smoking abstinence among ADHD smokers in comparison to non-ADHD smokers. In addition, abstinence-induced changes in emotion dysregulation are predicted to be associated with increasing the immediately reinforcing effects of cigarette smoking among those higher in ADHD symptoms. If these hypotheses are supported, this would suggest that treatment and prevention efforts for ADHD smokers need to target emotion dysregulation. Given that emotion dysregulation is a transdiagnostic construct, findings associated with ADHD can serve as a prototype for investigating the role of emotion dysregulation among other psychiatric populations with comorbid nicotine dependence.