The current study tested the hypothesis that substance abuse has features of both an internalizing and externalizing disorder. A confirmatory factor analysis (CFA) of data from 1,177 adjudicated delinquents supported a three-factor model (negative emotionality, fearlessness, and disinhibition) over alternate one- and two- (internalizing and externalizing) factor models; a second CFA indicated that self-reported offending and substance abuse formed separate dimensions rather than a single dimension. Correlating several temperament/personality indicators with measures of substance misuse and offending revealed that substance misuse was significantly more aligned with the internalizing dimension (i.e., negative emotionality) and significantly less aligned with the fearlessness externalizing dimension.