Unlike European or Caucasian subjects, Asians such as Koreans, Japanese and Chinese are known to rarely exhibit the 7-repeat allele of DRD4 exon III 48-bp VNTR polymorphism in exon III of the DRD4 gene.9,10 Accordingly, this study examines the distribution of DRD4 gene polymorphism and correlation with treatment responce in ADHD children in Korea. Here, DRD4 is linked to attention deficit-hyperactivity disorder.