Validity refers to the accuracy of measurement of the intended construct, or the degree to which evidence supports the interpretation of test scores for an intended use (American Educational Research Association [AERA], American Psychological Association [APA], & National Council on Measurement in Education [NCME], 2014). Multiple sources of validity must be considered when designing and evaluating a test. For test scores from the Conners Adult ADHD Rating Scales 2nd Edition (CAARS™ 2), validity evidence based on internal structure, relations with conceptually related constructs, and relations with criterion variables were investigated.