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Abstract Background and Objective: With regard to high prevalence of attention deficit hyperactivity disorder (ADHD) and its being significantly affected by nutritional factors, we aimed to determine the relationship between Ferritin serum level and ADHD. Material and methods: This ex-post- facto (causal comparative research) design study was conducted on 60 children, selected via convenience sampling. Thirty of them were ADHD children diagnosed by a psychiatrist using DSM IV checklist, as a case group, and the rest were healthy ones located in control group. Having their family informed consent, their Ferritin level was measured via ELIZA method. Results: The results show that Ferritin serum level of ADHD children are lower than that of healthy ones. Using t- test, it was indicated that the difference is significant (p= 0.002). Besides, the result of Pearson correlation coefficient showed that there is no significant relation between Ferritin and ADHD. Conclusion: In terms of the results and the importance of this issue, we recommend conducting further controlled research. Keywords: Ferritin, ADHD, Attention Deficit Hyperactivity Disorder