The validity of DSM-IV criteria for each subtype of ADHD was evaluated in 126 children, aged 4 through 6 years, and 126 matched controls at the University of Chicago. Children who met DSM-IV diagnostic criteria according to parent interviews and teacher reports differed from controls on a wide range of measures of social and academic impairment. Criteria for all three DSM subtypes were valid for identification of children with ADHD, aged 4 -6 years. 
COMMENT. DSM-IV criteria for subtypes of ADHD are valid in younger children, aged 4 through 6 years. All children diagnosed with ADHD showed significant functional impairments in behavior, attention, and social skills, and deficits in academic achievement.