Background: Obsessive–compulsive disorder (OCD) and attention-deficit and hyperactivity disorder (ADHD) frequently coexist. Childhood ADHD symptoms have negative impact of on the clinical presentation of OCD. Our aim is to evaluate the prevalence of childhood ADHD symptoms among OCD patients and the effect of this on clinical characteristics of the disorder. Methods:. We applied the Structured Clinical Interview for DSM-V to diagnose OCD on 100 OCD patients fulfilling our inclusion criteria .The Arabic-translated and validated version of the Wender Utah Rating Scale (WURS), was used to retrospectively assess childhood ADHD symptoms.The severity of OCD was assessed by the Yale–Brown Obsessive Compulsive Scale (Y-BOCS), severity of depression was assessed by the Hamilton Depression Rating Scale-17 (HDRS) and severity of anxiety was assessed by the Hamilton Anxiety Rating Scale (HAM-A). Barratt Impulsiveness Scale-11 (BIS-11) was used to assess impulsiveness . The adult ADHD was measured by the adult ADHD self-report scale Symptom Checklist. Results: 44% of the OCD patients had ADHD symptoms since childhood. Patients with childhood ADHD symptoms had an earlier onset of OCD, higher levels of depression, anxiety and impulsiveness. The scores of the Y-BOCS did not differ significantly between those having and not having childhood ADHD symptoms. Conclusion: Childhood history of ADHD symptoms is common in adult OCD patients. Childhood ADHD symptoms are associated with an earlier age of OCD, more severe depression, anxiety and higher impulsiveness.