Although attention deficit and hyperactivity disorder (ADHD) are recognized as neurodevelopmental disorders characterized by impairment in executive functions, impairments in social functioning are often accompanied by ADHD. Oxytocin (OT) has been investigated in a number of psychiatric disorders owing to its effects on social interactions. The aim of this study was to determine the relationship between aggression, empathy and OT levels in children with ADHD. Forty male patients with ADHD, ranging in age from 7 to 18 years, and 40 healthy age-matched and sex-matched individuals were included in this study. The patients and healthy controls filled in the Buss-Perry Aggression Questionnaire and Bryant's Empathy Index for Children and Adolescents; the Reading the Mind in the Eyes test was then completed. Blood samples were collected for OT at the beginning of the study. Lower serum OT levels were observed in patients with ADHD compared with the healthy controls. Moreover, there was a negative correlation between serum OT level and aggression scores and a positive correlation between the serum OT level and empathy scores in patients with ADHD. We conclude that OT may play a role in aggression and empathy skills, affecting the social life of those with ADHD. (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.