OBJECTIVES: The Child Bipolar Questionnaire 2.0 (CBQ 2.0) is a rapid screener with a Core Index subscale of symptom dimensions frequently reported in childhood-onset bipolar disorder (BD) and scoring algorithms for DSM-IV BD, with and without ADHD, and the proposed Narrow, Broad, and Core phenotypes. This report provides preliminary data on the reliability and validity of the CBQ 2.0- Korean version. METHODS: Core Index subscale to effectively predict diagnostic classification by structured interview was assessed using the Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version-Korean Version (K-SADS-PL-K). Test-retest and inter-rater reliabilities of the CBQ 2.0 were assessed. Correlation of Korean Child Behavior Checklist (K-CBCL) with CBQ 2.0-Korean version was performed. RESULTS: The CBQ 2.0 screening algorithms performed with a specificity of 66.7% and a sensitivity of 94.7% in classifying subjects with K-SADS-PL-K diagnosis of BD vs. no BD. The Core Index subscale had "good" agreement with K-SADS-PL-K diagnosis (Kappa=0.676) in identifying BD, ADHD-only, and no diagnosis. CONCLUSION: This preliminary data is from a sample derived from the child and adolescent psychiatric clinics. Further validation is needed with community based samples in which childhood-onset BD is rarer and diagnoses more diverse. The CBQ 2.0-Korean version shows potential for rapid and economically feasible identification of possible childhood-onset BD cases as defined by DSM-IV criteria as well as by alternate disease phenotypes