As a result of a high treatment attrition rate two significant changes were made from August 2005 to the New South Wales Department of Corrective Services custody-based intensive treatment programme for sexual offenders (CUBIT) that directly reflect advances in the field of sex offender treatment. This article outlines the rationale and outcomes of these changes. It is argued that the implementation of an open-ended (rolling) group treatment format has significant advantages over a closed group treatment format. Secondly, the programme is now emphasizing the importance of the use of positive therapist characteristics within the programme and in so doing has moved away from an overly manualized delivery of cognitive behaviour treatment. The positive outcomes produced by the changes are discussed. © 2008 The Australian and New Zealand Association of Psychiatry, Psychology and Law.