AbstractThe discriminant and concurrent validity of the Gordon Diagnostic System (GDS) was investigated in 29 youngsters categorized into “normals” or “ADHDs” based on teacher ratings. The results failed to demonstrate the discriminant validity of any GDS score regardless of the behavior rating used. The Vigilance Correct and Vigilance Omission scores were significantly correlated with ADHD Rating Scale scores completed by teachers. The sample size in the study demands cautious interpretation of these results; however, the authors suggest the continued use of multiple behavior ratings by teachers as the “gold standard” for the classification of youngsters with a suspected Attention‐deficit Hyperacti