Peer support programs in educational settings are growing in popularity, but few studies have applied a construct validity approach to test the relation of domain specificity between peer support and self-concept. In the present investigation, participation in different types of peer support program displayed differential impact on self-concept. In one study, participants who had received an academically-orientated peer tutoring program on verbal subject matter displayed significantly higher Verbal self-concept as measured by the Self Description Questionnaire II (SDQII) than those who had not participated in the program. In another study, participants who had received socially-orientated peer support program on improving interpersonal skills and communication displayed significantly higher Same-sex Relations self-concept as measured by Self Description Questionnaire II (SDQII) than those who had not participated in the program. In both studies, there were no significant effects on the other facets of self-concept. The findings were consistent over gender. This provided strong evidence of the relation of domain specificity between peer support and self-concept in that specific peer support shares a positive relation with specific domains of self-concept.