Recent research on the DSM-IV subtypes of attention-deficit/hyperactivity d
isorder (ADHD) has demonstrated that the subtypes differ in demographic cha
racteristics, types of functional impairment, and profiles of comorbidity w
ith other childhood disorders. However, little research has tested whether
the subtypes differ in underlying neuropsychological deficits. This study c
ompared the neuropsychological profiles of children without ADHD (n = 82) a
nd children who met symptom criteria for DSM-IV Predominantly Inattentive s
ubtype (ADHD-IA; n = 67), Predominantly Hyperactive Impulsive subtype (ADHD
-HI; n = 14), and Combined subtype (ADHD-C; n = 33) in the areas of process
ing speed, vigilance, and inhibition. We hypothesized that children with el
evations of inattention symptoms (ADHD-IA and ADHD-C) would be impaired on
measures of vigilance and processing speed, whereas children with significa
nt hyperactivity/impulsivity (ADHD-HI and ADHD-C) would be impaired on meas
ures of inhibition. Contrary to prediction, symptoms of inattention best pr
edicted performance on all dependent measures, and ADHD-IA and ADHD-C child
ren had similar profiles of impairment. In contrast, children with ADHD-HI
were not significantly impaired on any dependent measures once subclinical
symptoms of inattention were controlled. Our results do not support distinc
t neuropsychological deficits in ADHD-IA and ADHD-C children, and suggest t
hat symptoms of inattention, rather than symptoms of hyperactivity/impulsiv
ity, are associated with neuropsychological impairment.