We compared 2 rating scales with different manic symptom items on diagnostic accuracy for detecting pediatric bipolar spectrum disorder (BPSDs) in outpatient mental health clinics. Participants were 681 parents/guardians of eligible children (465 male, mean age = 9.34) who completed the Parent General Behavior Inventory-10-item Mania (PGBI-10 M) and mania subscale of the Child and Adolescent Symptom Inventory-Revised (CASI-4R). Diagnoses were based on KSADS interviews with parent and youth. Receiver operating characteristic (ROC) analyses and diagnostic likelihood ratios (DLRs) determined discriminative validity and provided clinical utility, respectively. Logistic regressions tested for incremental validity in the CASI-4R mania subscale and PGBI-10 M in predicting youth BPSD status above and beyond demographic and common diagnostic comorbidities. Both CASI-4R and PGBI-10 M scales significantly distinguished BPSD (N = 160) from other disorders (CASI-4R: Area under curve (AUC) = .80, p < 0.0005; PGBI-10 M: AUC = 0.79, p0.05). Diagnostic likelihood ratios indicated low scores on either scale (CASI: 0-5; PGBI-10 M: 0-6) cut BPSD odds to 1/5 of those with high scores (CASI DLR- = 0.17; PGBI-10 M DLR- = 0.18). High scores on either scale (CASI: 14+; PGBI-10 M: 20+) increased BPSD odds about fourfold (CASI DLR+ = 4.53; PGBI-10 M DLR+ = 3.97). Logistic regressions indicated the CASI-4R mania subscale and PGBI-10 M each provided incremental validity in predicting youth BPSD status. The CASI-4R is at least as valid as the PGBI-10 M to help identify BPSDs, and can be considered as part of an assessment battery to screen for pediatric BPSDs.