Objective: Symptoms of attention deficit hyperactivity disorder (ADHD) have been previously shown to be related with dopamine and noradrenaline dysfunction. Iron is the main cofactor of the tyrosine hydroxylase enzyme, the rate-limiting protein in dopamine synthesis. We aimed to investigate the association between iron/ferritin serum levels/subtypes and behavioral symptoms of ADHD. Methods: Fifty-eight children diagnosed with ADHD according to DSM-IV criteria in Samsun Ondokuz Mayis University Medical Faculty, Child Psychiatry out-patient clinic, were included in this study. Serum iron and ferritin levels in the participants were measured. The parents of the participants completed the Disruptive Behaviors Rating Scale-Parent Version (DBRS-PV).Results: There was no significant difference in serum iron and ferritin levels between the ADHD subtypes (p<0.05). We found a statistically significant negative correlation between the scores of DBRS-PV conduct problems and ferritin levels (r=-0.38, p<0.05). In further analysis, when participants age, gender, parental education level, ferritin and iron levels were taken into consideration, ferritin level was found the most powerful predictor of conduct score.Conclusion: This study revealed that serum ferritin level is significantly correlated with severity of conduct problems in children with ADHD. Especially in children with ADHD with low serum iron and ferritin levels, iron treatment would have beneficial effects on conduct problems comorbid with ADHD. (Archives of Neuropsychiatry 2011; 48: 125-8)