We tested the psychometric properties of the Hypomania Checklist (HCL-32) in a sample of nonclinical adolescents, examined the association with current psychopathology, and tested if "hypomanic" adolescents differ from other participants regarding HCL-scores and psychopathology. A total of 294 students completed the HCL-32 and the SDQ, a screening for psychopathology. In adolescence, the internal structure of hypomania seems to be represented by a triple structure. The first factor "active-elated" is an indicator of symptoms related to energy and activity. The adult factor "irritable-risk taking" is better reflected by two separate factors ("disinhibited/stimulation-seeking" and "irritable-erratic"). These factors were associated with externalizing problems. "Hypomanic" adolescents showed higher HCL total and disinhibited/stimulation-seeking scores and reported more conduct problems than "non-hypomanic" youngsters. The internal structure of the HCL in adolescents mirrors the association of juvenile bipolarity with substance use and symptoms of ADHD and conduct disorder and presents preliminary evidence for its validity. (Contains 2 tables.)