Abstract: Background and Objective: Attention Deficit Hyperactivity Disorder (ADHD) possesses lots of dysfunctions in biochemical component of brain. Some researchers proposed that examination of glial function require in ADHD. In this study, it is aimed to determine the serum levels of Glialy Fibrilar Acidic Protein (GFAP) and Nogo-A which were not investigated previously in children with ADHD. Methodology: Twenty eight children, aged 6-10, diagnosed with attention deficit hyperactivity disorder according to DSM-IV criteria and 28 healthy children matching in age and gender were included in the study. Children were assessed via Kiddie-Sads-Present and Lifetime Version, Turgay DSM-IV based child and adolescent behavior disorders screening and rating scale and Stroop test. Serum GFAP and Nogo-A levels were determined by enzyme-linked immunosorbent assay. Results: The GFAP and Nogo-A serum levels of children with ADHD were found to be significantly higher than those of controls. Moreover, serum Nogo-A levels showed a significantly positive correlation with Stroop interference in children with ADHD. Conclusion: These findings may provide evidence for neuroplasticity, microglial and astroglial changes in children with ADHD. It is recommended that investigation of cerebrospinal fluid and brain levels of GFAP and Nogo-A may contribute to the clarification of the pathophysiology of ADHD.