Hyperactive children are often said to be inattentive and distractible. However, the results from a number of experimental studies are equivocal. To examine this discrepancy, a Chinese version of the Stroop Test was devised. Four groups of subjects recruited from a community sample of 1479 Chinese boys living in Hong Kong took part in the investigation. These were: (1) a pure hyperactive (HA) group; (2) a mixed hyperactive/conduct-disordered (HA + CD) group; (3) a pure conduct-disordered (CD) group; and (4) a normal (N) control group. The results revealed that HA children were more markedly affected by the introduction of distracting stimuli. This distractibility was probably a function of both stimulus potency and the random order in which stimuli were presented. The specificity of a greater distractibility to HA children indicates its diagnostic value with regard to hyperactivity. The failure to find a similar deficit in HA + CD children raises questions about the clinical identity of this mixed diagnostic group.