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Objective: The current study investigated whether attention deficit hyperactivity disorder (ADHD) was associated with increased inflammatory response by assessing neutrophil/lymphocyte (NLR) and platelet/ lymphocyte ratios (PLR) which are new biomarkers of systemic inflammation in children with ADHD compared to healthy controls. Methods: In this study, 65 children in the ages of 6-11 years who were diagnosed with newly ADHD according to DSM-IV diagnostic criteria were included in the case group, whereas 65 healthy children without any psychiatric or physical disorder in the similar age and gender were included as the control group. The study group included 130 children with normal mental capacity, without known acute or chronic medical and/or inflammatory disease, and no concurrent drug use. Complete blood count analyses were made in the morning after 12 hour fasting, NLR and PLR were calculated using the absolute cell counts. Results: There was statistically significant difference in NLR, PLR and other complete blood count parameters between ADHD and healthy control groups. Higher MPV values de-tected in the case group were normalized after adjusting for comorbidity and body mass index values. Conclusion: Similar NLO and TLO values in the ADHD and healthy control groups do not support the hypothesis of increased inflammatory response involvement in the etiology of the disease. However, considering the heterogeneity about ADHDs clinical presentation and etiopathogenesis, it is clear that wide systematic follow up studies are needed in this area. [Anadolu Psikiyatri Derg 2019; 20(3.000): 313-320]