Deliberate self-harm is a serious health problem which is reported by around 3-11% of adolescents in Scandinavia. The prevalence is highest in the age of 15-19 years. Delibrate self-harm is defined as intentionally injuring oneself in a manner that ends in damage to body tissue, but without any conscious suicidal intention. Deliberate self-harm is associated with high suicidal risk, PTSD, eating disorder, substance use disorders and personality disorders. Some risk factors for deliberate self-harm are childhood sexual and physical abuse, neglect, insecure attachment with the caregiver and too early separation from the caregiver.Dialectical behaviour therapy is developed by Marsha M. Linehan, an American psychologist, to treat suicidal women with borderline personality disorder. The therapy method is based on cognitive behaviour therapy, dialectical and zen-buddhist thinking. DBT works through skill trainings in group, individual therapy and telephon conversation.Mentalization based therapy is a new therapy method which is developed by Anthony Bateman and Peter Fonagy for treatment of patient with borderline personality disorder. This model suggests that disruption of the attachment relationship early in development, in the first year of life, in combination with later traumatic experience in an attachment context causes impaired neurobiological developments.This combination causes hyper- responsiveness of the attachment system which makes mentalizing, and unstable behaviour during emotional overwhelm. These cause a relational malfunction, unstable self-structure and destructive behaviour in borderline personality disorder. Patient with BPD try to maintain self-structure with self harm. Bateman and Fonagy mean that the correction of some of these malfunctions can be achieved by assisting patients by recovery of mentalizing.