Objective: The aim of the study was to investigate the pattern of neuropsychological profiles on the Wechsler Adult Intelligence Scale–IV (WAIS-IV) for ADHD adults relative to randomly matched controls and to assess overall intellectual ability discrepancies of the Full Scale Intelligence Quotient (FSIQ) and the General Ability Index (GAI). Method: In all, 116 ADHD adults and 116 controls between 16 and 71 years were assessed. Results: Relative to controls, ADHD adults show significant decrements in subtests with working memory and processing speed demands with moderate to large effect sizes and a higher GAI in comparison with the FSIQ. Conclusion: This suggests first that deficits identified with previous WAIS versions are robust in ADHD adults and remain deficient when assessed with the WAIS-IV; second that the WAIS-IV reliably differentiates between patients and controls; and third that a reduction of the FSIQ is most likely due to a decrement in working memory and processing speed abilities. The findings have essential implications for the diagnostic process. (J. of Att. Dis. 2013; XX(X) 1-XX)