Children and adolescents with ADHD were evaluated with high-resolution brain SPECT imaging to determine if there were similarities between reported PET and QEEG findings. Fifty-four children and adolescents with ADHD by DSM-III-R and Conners Rating Scale criteria were evaluated. A non-ADHD control group was also studied with SPECT. Two brain SPECT studies were done on each group, a resting study and an intellectual stress study done while participants were doing a concentration task. Sixty-fiver percent of the ADHD group revealed decreased perfusion in the prefrontal cortex with intellectual stress, compared to only 5% of the control group. These are findings consistent with PET and QEEG findings. Of the ADHD group who did not show decreased perfusion, two-thirds had markedly decreased activity in the prefrontal cortices at rest.