The book argues the case for the usefulness of an empirically based understanding of the internal world of juvenile sex offenders as a way of humanely relating to their difficulties. It details the extent and nature of juvenile sex offending and its impact on victims and provides an extensive psychoanalytically oriented description of this offender group. The background of these offenders is examined, focusing on their experience of abuse, especially sexual abuse. Attention is paid to the unique characteristics of these offenders, particularly their attachment difficulties. The value of attachment theory and the concepts of psychopathy and malignant narcissism are then explored as a means of viewing their internal world. This internal world is also viewed through an empirical lens, which reveals them to have impaired psychic representations of human relationship, different needs for relationship and, in the most psychopathic group, an obfuscation of that need.The implications of these findings are then considered and the application of these understandings of their internal world is then explored. Firstly, issues related to assessment are addressed and, following detailed clinical case examples of their differences, their treatment needs are examined. In particular, the utility of a proposed modified version of Mentalization Based Therapy (MBT) is considered as part of a continuum of psychoanalytically oriented treatment options. Finally, there is a reflection on the reality that juvenile sex offending represents, with some concluding thoughts about addressing this ongoing and distressing problem.