Validity of the adolescent version of the World Health Organization Composite International Diagnostic Interview (CIDI) Version 3.0, a fully-structured research diagnostic interview designed to be used by trained lay interviewers, is assessed in comparison to independent clinical diagnoses based on the Schedule for Affective Disorders and Schizophrenia for School-age Children (K-SADS). This assessment is carried out in the clinical reappraisal sub-sample (n = 347) of the US National Comorbidity Survey Adolescent (NCS-A) supplement, a large (n = 10,148) community epidemiological survey of the prevalence and correlates of adolescent mental disorders in the United States. The diagnoses considered are panic disorder and phobic disorders (social phobia, specific phobia, agoraphobia). CIDI diagnoses are found to have good concordance with K-SADS diagnoses [area under the receiver operating characteristic curve (AUC) = 0.81–0.94], although the CIDI diagnoses are consistency somewhat higher than the K-SADS diagnoses. Data are also presented on criterion-level concordance in an effort to pinpoint CIDI question series that might be improved in future modifications of the instrument. Finally, data are presented on the factor structure of the fears associated with social phobia, the only disorder in this series where substantial controversy exists about disorder subtypes. Copyright © 2011 John Wiley & Sons, Ltd.