Distorted perceptions and attitudes related to an offender's criminal sexual behavior showed the strongest potential to distinguish those who failed to complete treatment from those who completed treatment. These distorted thinking patterns were used to deny, justify, minimize, and rationalize the behavior. Compared with offenders who completed treatment, those who left treatment had low scores on self-esteem measures. Future research should focus on how treatment can increase self-esteem and any link it might have to the capacity of an offender to critically assess the distorted thinking underlying his criminal sexual behavior. Study participants were 138 adolescent boys between the ages of 13 and 16 who were ordered by a court to participate in residential sex offender treatment. They were recruited from sex offender residential programs in both juvenile justice and mental health settings in the southeastern region of the United States. The assessment of cognitive distortion was measured by the Molest and Rape Scales developed by Bumby (1996). Sexual knowledge was measured with the Sexual Knowledge Questionnaire, and the Attitude and Value Inventory developed by Kirby (1984) assessed attitudes related to sexual behavior. Empathy was assessed with the Interpersonal Reactivity Index; and the Index of Self-Esteem measured the degree, severity, or magnitude of problems with self-esteem. 3 tables and 38 references