Since left motor preference has been hypothesized to lead to increased risk for psychopathology and cognitive deficits, it is possible that it may confer greater vulnerability for these problems to attention deficit hyperactivity disorder (ADHD) children. Subjects were 6-17 year-old boys with DSM-III-R ADHD (N = 140) and normal controls (N = 120) and their first-degree relatives. Information on motor preference was obtained in a standardized manner blind to the proband's clinical status. Although no excess of non-right motor preference was identified in ADHD probands compared with normal controls, the non-right motor preference observed in ADHD probands was partly familial and was associated with significantly increased risk for major depressive disorder and impaired psychosocial functioning. Non-right motor preference in ADHD probands significantly increases the risk for major depression and impaired psychosocial functioning. These findings raise the possibility of alterations in cerebral dominance which may be implicated in the expression of specific problems in some patients with ADHD. Further research is needed to replicate these findings and to directly assess cerebral functioning in ADHD.