Objective: The aim was to investigate how well neuropsychological measures can discriminate between adults with ADHD and those with other psychiatric disorders. Method: Adults with ADHD and a clinical control group (n = 110) were included. Neuropsychological functioning was investigated using measures of inhibition, working memory, set shifting, planning, fluency, reaction-time variability, and delay aversion. Results: Adults with ADHD performed more poorly compared with clinical controls with regard to all constructs. The effects of verbal memory, inhibition, set shifting, fluency, and delay aversion remained significant when controlling for IQ. However, when controlling for basic cognitive functions, only the effects of inhibition, fluency, and delay aversion were significant. Sensitivity ranged between 64% and 75%, and specificity between 66% and 81%. Conclusion: Neuropsychological tests have a relatively poor ability to discriminate between adults with ADHD and clinical controls, but they may be used to identify individuals at particularly high risk for poor daily functioning. (J. of Att. Dis. XXXX; XX(X) XX-XX)