Introduction: Conflicting findings exist regarding the link between attention deficit hyperactivity disorder (ADHD) and cardiovascular diseases. This study aimed to evaluate the frontal QRS-T (fQRS-T) angle and its correlation with symptom severity in children diagnosed with ADHD. Methods: The study population consisted of 172 patients diagnosed with ADHD (120 drug naive and 52 drug positive) and 82 healthy controls. ADHD symptoms were assessed using the Atilla Turgay DSM-IV-Based Screening and Assessment Scale for Disruptive Conduct Disorders (T-DSM-IV-Scale). The fQRS-T angle and corrected QT (QTc) interval were obtained from the automated reports of 12-lead electrocardiography device for each patient. Results: QTc interval and fQRS-T angle were significantly different among the groups. Post hoc analyses showed that QTc interval and fQRS-T angle of ADHD drug naive and ADHD drug positive patients were significantly higher than the healthy control groups. However, there was no significant difference between drug naive and drug positive patients regarding QTc interval and fQRS-T angle. Both QTc interval and fQRS-T angle showed positive correlations with the severity of ADHD symptoms (r = 0.263, p = 0.001 and r = 0.175, p = 0.023 respectively). Conclusion: We found that fQRS-T angle was significantly wider in children with ADHD. Therefore, we suggest that fQRS-T angle may help in cardiovascular risk assessment in children with ADHD.