The aim of this study was to examine the psychometric properties and clinical utility of the Children's Automatic Thoughts Scale (CATS; Schniering, C. A., & Rapee, R. M. (2002). Development and validation of a measure of children's automatic thoughts: The Children's Automatic Thoughts Scale. Behaviour Research and Therapy, 40, 1091-1109) in a large sample of anxious youth. The participants were 891 referred children and adolescents. Participants completed the CATS and a wide range of symptom measures, and were assessed via a structured diagnostic interview. Previous community-based psychometric properties were confirmed. The scale was highly sensitive to treatment change, and showed evidence of cognitive specificity with reductions in threat and failure beliefs, but not in hostility beliefs following treatment. The CATS demonstrated good convergent validity with related anxiety and depression scales, and moderate discriminant validity was found across anxious, anxious-depressed and anxious-oppositional groups. Implications for the assessment of child anxiety, and difficulties around children "faking good" on anxiety measures are discussed.