PURPOSE: This study was done to verify the reliability and validity of the Korean version of DMCI in Korean adolescents. METHODS: A methodological study design was used with Cronbach's alpha for reliability, and an exploratory factor analysis and contrasted groups approach for construct validity. DMCI was translated into Korean and tested with a sample of 406 adolescents in Korea. The data were analyzed using Cronbach's alpha, item correlation with total, principal component factor analysis, and t-test. RESULTS: The translated content of the DMCI was validated by nursing faculty members and translation equivalency was obtained. The Cronbach's alpha of the DMCI simplified with 18 items was .78. The factor analysis revealed three factors explaining 41.5% of total variance and the corresponding factors were self-observation (21.6%), self-judgement (11.4%), and self-confidence (8.6%). The mean score for the DMCI in the aggression group was significantly lower than the non-aggression group. CONCLUSION: Results of this study suggest that the Korean version of DMCI can used as a reliable and valid measure to assess decision making competency in Korean adolescents.