Attachment theory suggests that representations of previous attachment experiences may explain differences in psychosocial functioning. However, the nature of the association in clinical populations is unclear. Attachment representations were classified on the basis of Adult Attachment Interviews with 61 adolescents (13-20 years old; 70% female) admitted to a residential treatment institution. Group care workers rated their problem behavior. Compared to dismissing and autonomous adolescents and adolescents unresolved/disorganized with respect to trauma, adolescents with preoccupied attachment representations showed the highest levels of truancy and rule breaking, according to the institution's records, and externalizing behaviour, according to the group care workers. Unresolved/disorganized adolescents displayed lower levels of violence to staff than dismissing and autonomous adolescents. The effectiveness of residential treatment might be enhanced by taking account of the attachment strategies with which adolescents enter institutions.