Objective: The authors studied the hemispheric functioning of adolescents with attention-deficit hyperactivity disorder (ADHD) in relation to this group's response to positively toned emotional stimuli. Method: Dichotic word tests were used to measure perceptual asymmetry in 21 adolescent inpatients and 24 control subjects. Ten patients had ADHD; 11 did not. Subjects were tested under four emotional conditions by using combinations of neutral, positive, and negative words. Results: the ADHD group had lower right ear advantage (REA) scores when presented with stimulus pairs containing positive words than when presented with pairs not containing positive words. By comparison, the non-ADHD patient group and the control group had higher REA scores under positive emotional conditions than under non-positive conditions. Conclusions: The abnormal response to positive emotional tone supports the reward system dysfunction hypothesis of ADHD and may also have implications for learning problems, behavioral difficulties, and disturbed interpersonal relationships in this population.