OBJECTIVES: We investigated the factors related to the treatment outcome for substance abuse inpatients. METHODS: We reviewed the medical records of 97 patients who were discharged from the substance abuse treatment unit in Seoul National Mental Hospital. We then had follow-up telephone interview with 53 family memebers and/or patients of 97 patients. RESULTS: 1) Among 97 discharged patients, 59 patients were dropped out, 38 patients graduated successfully from the treatment program. The dropout group had shorter treatment period, were more often admitted involuntarily, had greater incidence of violence history and violated ward rules more often(p<.05). The main reasons for dropout were violation of rules(45.3%), escape during outdoor activities(3.7%), and refusal of return to the hospital(15.2%). 2) At the follow-up interview, 32 patients were abstaining from substances whereas 21 patients resumed use. The abuser group and more previous psychiatric admissions, more comorbid psychiatric disorders, and higher percentage of history of suicide attempts than the abstaining group(p<.05). 3) After the discharge from the hospital, 45% of patients showed to discontinue substance. Treatment graduates were more in recovery from substance abuse. The abstaining group had a higher percentage of employment than the abuser group(p<.05). CONCLUSION: The treatment outcome was more likely to be related with co-existing psychiatric problems such as previous psychiatric admission, comorbid psychiatric disorders, and history of suicide attempts. Therefore it is suggested that careful evaluation and appropriate treatment for such factors are needed for better treatment outcome. And psychiatric interview to enhance the motivation of patients is needed for completion of treatment.