Objective: This study was the first to investigate the efficacy of long wave infrared (LWIR) imaging as a diagnostic tool for ADHD. Method: with ADHD and a high level of specificity (94%) in discriminating those with ADHD from those with other diagnoses. The overall classification rate was 73.16%. This was indicative of a high level of discriminant validity in distinguishing between patients with and without ADHD. There was a moderate level of agreement between LWIR imaging and multiple other diagnostic tests for ADHD. Conclusions: LWIR imaging demonstrated high sensitivity and specificity as a diagnostic tool for ADHD. These results provide evidence for the efficacy of a novel, quick, and effective way to investigate the physiological basis of one of the most prevalent childhood psychiatric disorders. (Contains 1 table and 2 figures.)