Objective: Attention deficit hyperactivity disorder (ADHD) is the most common neuropsychiatric disorder seen in childhood. It is characterized by inattention, hyperactivity, and impulsivity that is inappropriate for the age and developmental level of the child. Although the number of studies investigating the neurobiological basis of ADHD is increasing, there is still no clear understanding of the mechanisms of the disorder. Serum copper and ceruloplasmin levels may play a role in the neurobiology of ADHD due to their effects on oxidative mechanisms and the dopaminergic-catecholaminergic system. However, the results of studies investigating the serum levels of copper in patients with ADHD are contradictory. Moreover, serum ceruloplasmin levels have not yet been studied. The aim of the current study was to compare the serum copper and ceruloplasmin levels in children and adolescents with ADHD to the levels found in healthy controls.