The present study evaluated the utility of parent- and child-reported social fears for reaching a diagnosis of social phobia in youth. The diagnostic utility of (a) the number of fears and (b) specific feared social situations was examined. The sample included 140 youth and their parents: youth diagnosed with social phobia (n = 50), youth diagnosed with generalized anxiety disorder or separation anxiety disorder but not social phobia (n = 49), and youth without an anxiety disorder (n = 41). Youth and their parents were interviewed separately using the Anxiety Disorders Interview Schedule for Children and Parents. Analyses indicate that a cut score of 4 parent-endorsed social fears optimally distinguished youth with and without social phobia. Analyses of child-reported fears did not identify a meaningful cut score. Conditional probability and odds ratio analyses indicated that several specific social fears have high diagnostic efficiency, and others were found to have limited diagnostic efficiency. Results are discussed with regard to informing diagnostic interviews and diagnostic systems for social phobia in youth.