Relations between self-concept and mental health are best understood from a multidimensional perspective. For responses by 903 adolescents (mean age = 12.6) to a new French translation of the Self Description Questionnaire II (SDQII), confirmatory factor analysis demonstrated a well-defined multidimensional factor structure of reliable, highly differentiated self-concept factors. Correlations between 11 SDQII factors and 7 mental health problems (Youth Self-Report; YSR) varied substantially (.11 to -.83; mean r = -.35). Single higher-order factors could not explain relations among SDQII factors, among YSR factors, or between the SDQII and YSR factors. This highly differentiated multivariate pattern of relations supports a multidimensional perspective of self-concept, not the unidimensional perspective still prevalent in mental health research and assessment.