This study examined gender differences in a range of lifetime psychiatric disorders in a sample of 272 offenders newly admitted to a prison substance abuse program. Although these men and women did not differ in severity of substance use in the six months prior to incarceration, women were significantly more likely than men to report a lifetime psychiatric disorder and a lifetime severe disorder. Furthermore, gender differences emerged in the pattern of lifetime psychiatric comorbidity. Women reported greater lifetime major depression, posttraumatic stress disorder, eating disorder, and borderline personality disorder; men were more likely than women to meet criteria for antisocial personality disorder. Additionally, female offenders were found to have a higher degree of internalizing disorders than male offenders, but there were no gender differences in degree of externalizing disorders. The study concluded that women offenders newly admitted to a prison substance abuse program present with a greater psychiatric vulnerability and a different pattern of psychiatric comorbidity than their male counterparts. Copyright © 2008 John Wiley & Sons, Ltd.