The present study compares the responses to treatment of sex offenders with intellectual disability receiving 1- and 2-year probationary sentences. There were seven subjects in each group. There were no differences between subjects with regard to age, IQ or previous offences. All subjects received group treatment which addressed issues of: denial, minimization and responsibility for the offence; harm done to the victim; behaviour consistent with offending; and victim awareness and confidentiality. The subjects were assessed on a standard questionnaire designed to assess attitudes consistent with sex offending. All subjects were convicted of either indecent exposure or offences against children. There was a significant difference between the groups at the end of the probation period with subjects sentenced to 2 years' probation showing greater improvement. Subjects receiving 1 years' probation retained a number of attitudes consistent with denial and minimization of their offence. Furthermore, follow-up data underlined the poorer response to treatment for the 1-year probation group in terms of re-offending rates and assessment of attitudes consistent with sex offending. The authors recommend that a court order for a 1-year period of probation with treatment is of little value when dealing with sex offenders with intellectual disability. Rather, a period of at least 2 years' probation with a treatment recommendation is suggested.