Objective: The aim of this case-controlled study is to evaluate chronic inflammation, subclinical atherosclerosis and cardiovascular disease risk in children and adolescents with ADHD. Methods: A total of 51 medication-free children and adolescents with ADHD and 51 healthy controls were included in this study. K-SADS-PL was used to determine the diagnosis of ADHD and other psychiatric disorders. Conners’ Parent Rating Scale-Revised Short Form and the Conners’ Teacher Rating Scale-Revised Short Form severity of ADHD was used to evaluate severity of ADHD. In order to evaluate subclinical atherosclerosis, common carotid intima media thickness (IMT), epicardial adipose tissue thickness (EAT), and periaortic adipose tissue thickness (PAT) were assessed as well as clinical parameters. Results: The IMT (0.037 ± 0.005 cm vs. 0.026 ± 0.003 cm), EAT (0.472 ± 0.076 cm vs. 0.355 ± 0.051 cm), and PAT (0.135 ± 0.016 cm vs. 0.118 ± 0.009 cm) measurements were significantly higher in the ADHD group than in the control group. Additionally, partial correlation analyses revealed that a positive correlation was observed between IMT and EAT, and PAT measurements separately. Multivariate linear regression analysis revealed that, body mass index (BMI) positively predicted IMT. Also, age and BMI positively predicted the EAT levels of the subjects with ADHD. Conclusion Our results suggest that children and adolescents with ADHD have a risk for cardiovascular disease. For this reason, subclinical atherosclerosis should be taken into consideration in the follow-up and treatment of ADHD for cardiovascular disease risk.