This study compared the treatment response of four groups of psychiatrically diverse opiate-dependent, methadone maintenance patients receiving drug counseling. The four groups were patients with no other nonsubstance abuse axis I psychiatric diagnoses (OP only; N = 65), patients with lifetime major depression (DEP; N = 60), patients with both antisocial personality disorder and lifetime major depression (APD + DEP; N = 35), and patients with only APD (APD only; N = 24). Patients were assessed at intake, during treatment, and 7 months after treatment admission. No statistically significant differences were found among the groups in treatment retention/attendance. Few significant group differences were revealed during-treatment urine screens, except that barbiturate use was more common for the APD only group. The APD only group also had significantly more positive urine screens for benzodiazepines than the other three groups at 7-month follow-up. All groups reported considerable improvement in problem level at 7 months compared with admission status. The APD only group reported fewer gains in legal and employment problems than the other groups but reported greater improvement in the drug area. Thus, there was some limited support for a prior finding, based on individual psychotherapy, that the treatment response of APD only patients was inferior to that of APD + DEP patients or non-APD patients.