Background: Attention deficit hyperactivity disorder (ADHD) etiology is not completely understood, but common comorbid dysfunction of immune system suggest that these systems may be affected by common genetic background and molecular mechanism, for example, increase levels of specific cytokines are observed in ADHD. The aim of this study was to evaluate the level of inerleukin-2 (IL-2) as a biomarker of ADHD and find out the relation between interleukin-2 and ADHD symptoms. Patients and Methods: A case control study carried out on 90 children who assigned into two equal groups: ADHD patients: met diagnosis of ADHD according to DSM V criteria and a control group. All groups were subjected to full history taken, thorough clinical examination , and measurement of Human IL-2 by ELISA technique. Results: The mean value of IL2 level was statistically significantly higher among ADHD cases than control group (p