OBJECTIVES: To assess the cost effectiveness of risperidone LAI compared with oral risperidone and oral olanzapine over a 1-year time period in outpatient with schizophrenia who had previously suffered a relapse requiring hospitalization as south Korea healthcare system. METHODS: Published medical literature and hospital electronic data were used to populate a decision-analysis model comparing the three treatment alternatives. The model captures: rates, frequency, duration of hospitalization, stable days(duration of out-patient follow-up) that healthcare resource utilization and associated costs. Primary outcomes were: the proportion of patient re-hospitalization; the frequency of hospitalization per patient; the number of hospitalization days per patient; the number of stable days and total direct and indirect cost per patient per years. Costs are in year 2007 Korea Wons. RESULTS: Based on model projections, the proportions of patients experiencing re-hospitalization after 1 year treatment were 19.0% for risperidone LAI, 25.0% oral olanzapine and 26.6% for oral risperidone, respectively. The mean number of days of re-hospitalization per patient per year was 16.6 for risperidone LAI, 21.9 oral olanzapine and 23.1 for oral risperidone, respectively. This would translate into total cost savings with risperidone LAI compared with oral olanzapine of 46,011, while oral risperidone more spend 78,905 respectively. The result of sensitivity analyses, patients re-hospitalization rate during 6-month treatment were total cost savings with risperidone LAI compared with oral risperidone and oral olanzapine. When drug cost of risperidone LAI, reducing 30% and 75%, compared with oral risperidone and oral olanzapine are cost- effective medicine. CONCLUSIONS: The use of risperidone LAI for treatment of outpatient with schizophrenia is predicted in this model to result in better clinical outcomes but higher total healthcare costs over 1 year than its comparators, oral risperidone and oral olanzapine. Risperidone LAI may therefore be carefully therapeutic option for outpatients with schizophrenia in the republic of Korea healthcare setting.