Children with attention deficit hyperactivity disorder (ADHD) display many behaviors consistent with an underlying deficit in executive processes. This study examines Norman and Shallice's (1986) supervisory attentional system (SAS) as an approximation of executive functioning thought to be impaired in ADHD. Fifteen ADHD children were compared to a clinical control sample of learning disabled (LD) children and control children matched for age, gender, and IQ on a series of tasks designed to tap the functions of the SAS. The tasks assessed either the inhibition of a strongly triggered response (Star Counting Test, Hayling Sentence Completion Test, and the Random Generation Test) or impulsive responding in the absence of strong trigger-schema contingencies (Brixton Spatial Anticipation Test). Analyses revealed that the ADHD group was significantly impaired, in comparison to the LD and control groups, on tasks requiring the inhibition of a strongly triggered response. Further support for the fractionation of the SAS is provided by the differential performance of the groups on these tasks.