The effectiveness of a Familyships Treatment Module offered at a medium security federal institution was explored. The Module was designed to help inmates build social skills to deal with dysfunctional family systems. Participants included sexual offenders and inmates convicted of other types of offenses. For the study, a measure of co-dependency that relates to personality deficiencies common to sex offenders was administered to forty-six inmates. Results from analysis of covariance indicate that, for both inmate groups studied, the higher the level of co-dependency, the greater the benefit from the treatment program. The Module was found to be most effective for offenders with severe levels of social dysfunction. Perhaps a less intensive approach could be established for inmates with less severe dysfunction. Findings demonstrate that, in the treatment of sex offenders, it is useful to explore offender background variables to better distinguish those who would benefit most from the Familyships Module.