The Continuous Performance Task (CPT) has become a popular research tool used to distinguish children with Attention-Deficit-Hyperactivity Disorder (ADHD) from their normal peers. Whether hyperactive children have a vigilance decrement remains an ongoing controversy. The theoretical basis of the CPT and variables known to influence performance are examined in order to interpret the inconsistencies evident in the research. Studies which employed the CPT in order to examine the possibility of sustained attention deficits in children with ADHD will be reviewed. The results are examined in light of group selection criteria, task variables and situational and external variables. It is concluded that there is no compelling evidence for a sustained deficit in ADHD children. An alternative theoretical model for understanding the results of CPT performance in ADHD children is provided.