Objective: It is known that adult attention deficit hyperactivity disorder (ADHD) starts in childhood and goes on in adulthood. Although the severity of the symptoms in ADHD decreases by growing up or symptoms change their form, problems in functioning go on. The aim of this study is to search comorbidity and functioning degree in adults with ADHD. Methods: According to DSM-IV TR diognosis criteria, 40 adult patients with ADHD (aged between 18-44, 52% male, mean age: 26.5±8.6) and 40 healty controls (aged between 18-36, 55 % male, aver-age age: 25±4.51) matched with those in terms of age and sex are taken into evaluation. Sociodemographic Data Form, SCID I, Wender Utah Rating Scale, Hamilton Depression Rating Scale Hamilton Anxiety Rating Scale, Young Mani Rating Scale, Social Adaptation Self-Assessment Scale, SCL-90 (Symptom Check-List) are applied to whom with ADHD and the control group. Cases are evaluated by a second expert in terms of ADHD diagnosis. Results: Comorbidity rate in adults with ADHD, which is determined with SCID-I, is rather high. Comorbidity group found most are mood disorders (50%) (22.5% major depression, 22.5% bipolar disorder, 5% distimic disorder). This is followed by common anxiety disorder (22.5%), obsessive compulsive disorder (7.5%) and panic disorder (7.5%). It is found that functioning degree of the ones whose ADHD sypmtoms are severe in childhood is lower in adulthood. Among ADHD subtypes, any difference is not found in terms of scale points and functioning. Conclusion: ADHD is frequently accompanied with axis I diognosis in adulthood and functioning of these cases are affected negatively. It is very important to evaluate the patients whose ADHD goes on in adulthood in terms of comorbidity and to cure of whom in terms of ADHD. [Anadolu Psikiyatri Derg 2011; 12(3.000): 185-191]