This study was conducted to examine the neuropsychological deficits in children with obsessive compulsive disorder (OCD). Furthermore, the focus of present study was to explore whether OCD children show the same executive dysfunction as adult OCD patients. The participants consisted of 106 children between the ages of 6 and 16 years who visited the department of child-adolescent psychiatry, Seoul National University Children's Hospital (17 OCD, 25 ADHD, 21 tic disorder, 20 depressive disorder, and 23 healthy children). The OCD children showed higher verbal ability compared to other psychiatric groups, but performed the worst on WISC-R subtests assessing perceptual organization ability under time pressure. The OCD children did not show any significant deficits in verbal intellectual function, memory, attention and concentration abilities. However, similar to the ADHD children, the OCD children had significantly more errors and completed fewer categories on the WCST compared to the healthy group. Through neuropsychological tests, the OCD children showed cognitive strength and weakness similar to those of OCD adults that were reported in previous research. Specifically, they had executive function deficits in mental set shifting, supporting the frontal-striatal dysfunction hypothesis of OCD in children as well as in adults.