Objective: In this study, we examined the sensitivity and specificity of the Conners’ Adult ADHD Rating Scale–Self-Report: Long Version (CAARS) in 113 adult clinical archival records. Method: Forty-five clients had requested evaluation for ADHD, suggesting problems with attention, and 68 requested other services. To examine the CAARS’ ability to differentiate ADHD symptoms from other Axis I symptoms, it was compared with the Personality Assessment Inventory. Results: The two groups differed significantly on the weighted linear combination of the eight subscales of the CAARS, Wilks’s Lambda = .565, F(7, 105) = 11.56, p < .0001, with higher mean scores found among those requesting evaluation of ADHD. z-tests revealed the eight CAARS subscales were more highly correlated with each other, based on the average intercorrelation, than the nine selected clinical scales of the Personality Assessment Inventory (PAI; Somatic Complaints [SOM], Mania [MAN], Paranoia [PAR], Schizophrenia [SCZ], Anxiety [ANX], Anxiety-Related Disorders [ARD], Depression [DEP], Borderline Features [BOR], and Antisocial Features [ANT]). Some unexpectedly high correlations were found between the CAARS and PAI clinical scales (MAN and SCZ). Conclusion: The results of the present study were mixed, with some analyses yielding positive results with respect to the CAARS’ sensitivity and others suggesting poor specificity.