This article presents a validation of a French questionnaire which has the objective of measuring the self-concept of pupils aged from 10 to 12. The Questionnaire de description de soi (QDS) is based on a translation of the Self-Description Questionnaire-I (SDQ-I) developed by Marsh (1988). The initial instru ment, enriched by new dimensions and items, was administered in 24 classes of grades 5 and/or 6 (n = 450). The analyses conducted on the data show interesting psyhometric properties and partly join former research results.