Using a within-subject design and both high- and low-interest tasks, this study examined the effects of reward (R), response cost (RC), and no contingency (NR) on performance and motivation of 22 children with attention deficit-hyperactivity disorder (ADHD) and 22 controls. Dependent variables included performance measures, self-rated performance and motivation, and a new measure of behavioral motivation based on a 2-min postcontingency task. Both contingencies benefited some aspects of the performance of ADHD children; relative to R, RC showed stronger effects but at the expense of decreased self-rated motivation on the low-interest task. The performance of controls did not differ across tasks, whereas ADHD children performed relatively better on the high-interest task. Neither contingency decreased motivation measures relative to NR for either group. For ADHD children, motivational effects appeared to be influenced by self-perceptions of performance.