The hypothesis testing behaviors of 50 boys with Attention-Deficit Hyperactivity Disorder (ADHD) were compared to those of 50 boys without ADHD. The two groups were randomly assigned to one of two feedback conditions: a) boys in the "instruction and rule" condition learned additional strategies to aid their performance on the Wisconsin Card Sorting Test (WCST); b) children in the "verbal only" condition learned no additional strategies. There were no significant group or condition differences between the boys on the primary dependent measures used. The results from the WCST were also evaluated according to five aspects of problem solving: (a) selective attention, (b) stimulus differentiation, (c) response generation, (d) response execution, and (e) responding appropriately to feedback. The study showed a tendency for the children with ADHD to respond according to a position or hypothesis set. Similarly, children in the "verbal only" condition tended to respond to feedback less appropriately than did children in the instruction and rule condition. These tendencies however, did not differentiate between the boys with ADHD and boys without ADHD.