Objectives This study aimed to assess the prevalence of bipolar spectrum disorders among Korean high school students (individuals in late adolescence) using the Korean version of the Mood Disorder Questionnaire (K-MDQ). Methods Two thousand male and female participants were proportionately selected from among high school students nationwide. From November 2007 through February 2008, we conducted an epidemiological survey of, and administered the K-MDQ to, these participants, assessed their psychometric properties, and compared characteristics between K-MDQ-positive and K-MDQ-negative participants. Results The K-MDQ’s internal consistency (Cronbach’s alpha) was 0.74. The item-total score correlations ranged from 0.35 to 0.57, and all were statistically significant (p<.001). Factor analysis with varimax rotation revealed 3 factors that explained 42.6% of total variance. We found the cutoff endorsement of the K-MDQ score (7 or more in criteria 1) in 1207 students (60.4%) and found 104 (5.2%) subjects were K-MDQ-positive, meeting all 3 K-MDQ criteria. The mean K-MDQ total score was 7.2±2.9 and total scores of K-MDQ-positives and K-MDQ-negatives were 9.9±1.7 and 7.0±2.9, respectively. K-MDQ-positives and K-MDQ-negatives showed no differences in the sociodemographic variables we assessed. Endorsement of items in total subject ranged from 15.7% to 77.7%. All items except item 8 (more energy) differed significantly in endorsement between K-MDQ-positives and K-MDQ-negatives. Items accounting for over 30% of the endorsement differences between K-MDQ-positives and K-MDQ-negatives were“feel so good,” “so irritable,” and“excessive, foolish, risky behavior.” Conclusion The K-MDQ was a relatively valid screening tool for Korean high school students. Per the result of the K-MDQ survey, suspected lifetime prevalence of bipolar spectrum disorders for those in late adolescence (high school students) seems to be 5.2%, suggesting that systemic screening for bipolar spectrum disorder should be required for this age group.