Objectives : The K-ARS (Korean ADHD Rating Scale) is one of the most important assessment tool of attention-deficit hyperactivity disorder (ADHD) in Korea. in this study, we presented detailed normative data on the K-ARS for school-aged children in Seoul metropolitan area to put it to practical use. Methods : The subjects were 2,397 students(1,223 boys and 1,174 girls, aged 6-12) from 4 elementary schools in Seoul, and one caretaker of each child completed the K-ARS for parents. Children who showed high scores of the K-ARS for parents were screened, and 2 child psychiatrists interviewed them to make a clinical diagnosis. We compared the mean scores of the K-ARS for parents between ADHD and normal group, and examined the percentage of correct classification. Results : There were some differences in score of the K-ARS for parents according to sex and age, so we presented continuous normative data with T score and subdivided cut-off points for ADHD screening. Interviews with child psychiatrists using DSM-IV criteria were performed to test diagnostic validity, and the difference in every the K-ARS for parents index between ADHD and normal group was significant(p<.001). Using 3 different cut-of points(80th, 90th, 93rd percentage), the accuracies of ADHD correct classification were 67.9, 72.2, 71.1% and all 3 canonical discriminants were significant (p<.05) between ADHD and normal group. Conclusion : The normative data and cut-off points on the K-ARS for parents are useful in screening ADHD children in Seoul metropolitan area.