Introduction: With regard to the internal/external frame of reference model of academic self-concept development the present study aimed at testing its theoretical assumptions within the verbal domain--namely to analyze the relations between achievement and self-concept in the native language German (L1) and the foreign language English (L2). Due to inconsistent research findings in this field the focus of analyses was on identifying differential patterns of dimensional comparison processes as they might depend on students' achievement level in both subject areas and on students' gender. Method: Data were gathered in a sample of 256 ninth grade students from German inner-city grammar schools. For measuring students' self-concepts two subject-specific scales were used. For measuring their achievement in each language subject latest grades as well as teacher competency ratings were used. Relations among constructs were analyzed by means of a structural equation modeling approach including multiple group comparisons between the female and male subsample. Results: No dimensional comparison effects could be demonstrated. Neither negative contrasting nor positive assimilation effects across both language subjects occurred. Furthermore, multiple group comparisons of structural equation analyses lent strong support for the invariance model. Thus, despite significantly apparent achievement and self-concept differences between female and male learners in the L1 German gender did not moderate the relations between achievement and self-concept variables across both language subjects. Discussion: In the female as well as in the male subsample self-concept formation in both language subjects appears to be mainly affected by social comparison effects. This finding not only confirms previous research results in the field, but also contributes to clarify the role of gender in the internal/external frame of reference model--concerning the issue of dimensional comparison within the verbal domain, at least. (Contains 4 tables and 2 figures.)