Objective: To validate the Catalan adaptation of the Conners’ Adult ADHD Rating Scales (CAARS), short version (self-report: CAARS-S:S; observer: CAARS-O:S). Method: A community sample of 424 adults responded to the two forms. Confirmatory factor analysis was used to test the dimensional structure. Results: The hypothesized four-factor model (Inattention/Memory Problems, Hyperactivity/Restlessness, Impulsivity/Emotional Lability, and Problems With Self-Concept) presented an adequate fit for the self-report and observer forms. Reliability was slightly higher for the CAARS-O:S (average α = .78) than for the CAARS-S:S (average α = .75). Test–retest average correlations were r = .80 (self-reports) and r = .73 (observer ratings). Informant agreement was high at test (average r = .59) and retest (average r = .61). There were significant gender and age differences. Conclusion: This adaptation of the two short forms of the CAARS-S presents adequate evidence of validity and reliability, and it can therefore be used for diagnostic purposes and cross-cultural comparisons. (J. of Att. Dis. 2012; XX(X) 1-XX)