The impact of personal construct and psychodynamic group work on the psychosocial functioning of offender adolescents was evaluated. The repeated measures design involved 3 data collections. Data from 102 participants included measures of 5 pairs of maturational processes and 5 psychological states. Group work was effective immediately after terminating treatment in increasing helpful maturational processes and in reducing the less helpful maturational processes. The group work was also effective to some extent in reducing less helpful psychological states. The implications of this research for future interventions and its evaluation are discussed.