The present study used a self-reporting questionnaire to compare suicide risk in outpatients being treated for substance use disorder at specialized hospitals to suicide risk in outpatients being treated for depressive disorder at general psychiatric clinics. Although patients in both groups exhibited an equal severity of depression, the patients with drug use disorder had a higher suicide risk than those with depressive disorder. These findings indicate that drug-abusing patients at specialized hospitals may have a severe risk of committing suicide, suggesting that carefully assessing the comorbidity of depression with drug abuse may be required for preventing suicide in drug-abusing patients.