Objectives : The purpose of this study was to investigate the deficits in executive function in children with ADHD and anxiety disorder, and further, to characterize executive function deficits among the two groups. Methods : Subjects consisted of 60 children between the ages of 5 and 14 (16 Normal, 24 ADHD, 20 Anxiety Disorder). Neuropsychological tests (KEDI-WISC, CCTT, STROOP, WCST, ROCF) for assessing cognitive and executive function were individually administered to all subjects. Results : There were no significant differences in FSIQ or PIQ among the three groups. However, the ADHD group tended to score lower on the VIQ and subtest of similarity, vocabulary, and digit span tests. The three groups did not significantly differ with respect to CCTT test results. On the STROOP test, the ADHD group showed poor performance on the word, color, and color-word subtests. The three groups did not exhibit significant differences in WCST test results ; however, the anxiety group performed poorly belonging to below 25 percentile rank on perseverative response. On the ROCF test, the ADHD group performed poorly with respect to their organization score and in particular, regarding copy and immediate recall. The anxiety group also performed poorly with regard to organization ; however, this was limited only to immediate recall. Conclusion : Children with ADHD displayed poor inhibition and organizational abilities compared to children with anxiety and normal controls. Further, children with anxiety disorder exhibited low cognitive flexibility and voluntary problem-solving abilities compared to ADHD children and normal controls. Based on these results, we suggest that the characteristics of executive dysfunction in ADHD and anxiety disorder in children are different.