Recent behavioral and neuropharmacological evidence suggests that the differentiation of children with Attention Deficit Disorder with (ADD/H) and without hyperactivity (ADD/WO) may reflect an appropriate nosological distinction. There is also evidence that attention-regulatory mechanisms possibly associated with anterior-posterior processes may be independently implicated in these children. To test this hypothesis, 100 clinic-referred children were reliably diagnosed as ADD/H (n = 48). ADD/WO (n = 26) and as having an internalizing disorder (n = 26) for inclusion as a clinic-control (CC) group. An analysis of covariance using Full-Scale IQ, chronological age, and the number of conduct-disorder symptoms provided little support for such a behavioral distinction using selected WISC-R, Luria-Nebraska-Children's Revision, and reaction-time variables. Alternative conceptualizations, possibly reflecting deficient right-hemispheric processes in ADD/H, may provide more productive avenues for research in distinguishing deficient neurocognitive processes in subtypes of ADD.