The objectives of this study were to provide a basic tool for pediatricians or other physicians to suspect and detect ODD in children with ADHD and to distinguish the symptomatic profile of ODD from ADHD. 101 subjects with ADHD, 83 with both ADHD and ODD and 342 controls aged 8 to 15 years were included in the study. A semi-structured interview was performed for evaluation of psychiatric diagnoses. Both parents and teachers completed DSM-IV Disruptive Behavior Disorders Rating Scale. We found differences among all three diagnostic subsamples in two-by-two analyses for all dimensions (Inattention, Hyperactivity/Impulsivity and ODD) both according to parent and teacher reports (p < 0.03 for all analyses). Based on parental ODD scores, ROC Curve analyses between 'only ADHD' and 'ADHD+ODD' groups showed that AUC was equal 0.80 (95%CI = 0.73-0.86) and the best cutoff point for ODD diagnosis in the ADHD subjects was 0.68. This study demonstrates the presence of a basic tool for detection and suspicion of ODD in children with ADHD for primary care clinicians or pediatricians in clinical settings. Findings also indicate that patients with ODD and ADHD have more severe inattention, hyperactivity/impulsivity and oppositional symptoms than those with only ADHD have.