Objective: Because of the interrelation between attention deficit hyperactivity disorder (ADHD) and substance use disorders (SUD), clinicians should consider ADHD comorbidity in assessment and treatment phase when evaluating adult substance dependence. It was aimed to compare the adult substance dependent patients with comorbid ADHD (ADHD+) and without comorbid ADHD (ADHD-) in terms of clinical features, psychiatric comorbidity and de-gree of functioning. Methods: 226 patients with substance dependence were included in the study (ADHD-=140, ADHD+=86). Diagnostic interview with SCID-I was performed. Adult ADD/ADHD DSM IV-Based Diagnostic Screening and Rating Scale, Wender Utah Rating Scale, Barratt Impulsivity Scale-11, Personal and Social Perfor-mance Scale were applied. ADHD+ and ADHD- groups were compared in terms of clinical features of substance dependence, psychiatric comorbidity and scale outcomes. Results: The group of ADHD+ was starting using sub-stance at an earlier age. Polysubstance use, number of days of substance use, and legal issues related to the substance were higher than the ADHD- group. ADHD+ group had more stimulant, opiate dependency. Rates of suicidal ideation and attempts, psychiatric comorbidity were higher in ADHD+ group. Personal and social functioning of ADHD+ group was worse. Discussion: ADHD+ group differs from the ADHD- group in terms of the clinical char-acteristics associated with the substance. In adults, there is a need for randomized, longitudinal follow-up studies involving both genders, investigating the effect of ADHD on SUD. [Anadolu Psikiyatri Derg 2019; 20(3.000): 296-304]