Sustained attention and inhibitory control of 15 nonhyperactive, learning disabled (LD) boys, 15 hyperactive but not LD boys, and 15 normal boys (11-12 years old) were studied, on teacher ratings of impulse control in the classroom and testing results. Coming to attention, decision making, sustained attention, and attention-concentration were measured by the "Children's Embedded Figures Test,""Matching Familiar Figures Test,""Children's Checking Task," and a subtest of the "Wechsler Intelligence Scale for Children-Revised." Normal children were found to be superior to both clinical groups in attentional processing, while hyperactive children encountered more errors than their LD peers on those tasks involving sustained attention. The finding that teachers rated hyperactives as more impulsive than nonhyperactive LD children was interpreted to explain why hyperactives are generally singled out first and identified for specialized treatment. Findings were also interpreted as supporting the "passive learner" hypothesis for LD children, which often accounts for their poor academic functioning. (Author/SEW)