The present study evaluated an alternative method of neuropsychological test interpretation for the classification of Attention-Deficit/Hyperactivity Disorder (ADHD) in adults. Specifically, an intra-individual discrepancy analysis was implemented in which differences between intellectual functioning and performance on a battery of six frontal/executive tests were examined within a homogeneous group of ADHD adults and matched normal controls. Significant group differences were identified between the ADHD adults and control sample on each of the dependent measures, with moderate diagnostic efficiency rates for the individual measures and a Discrepancy Impairment Index (DII). The discrepancy analysis approach generated significantly greater sensitivity in detecting the presence of ADHD as compared to a level of performance interpretive approach. Overall, these results provide support for the consideration of discrepancies between intellectual ability and frontal/executive functioning for the assessment of adult ADHD.