Background: The purpose of this study was to analyze the medical expense change and influencing factors after introducing longterm care insurance system. The study period was 2 years before and after introduction of the system. Methods: We analyzed data collected from two divided group lived in Incheon. Four hundred and eighty-five elderly who received long-term care wage for one year were selected for experimental group. For control group, 1,940 elderly were selected by gender and age stratified random sampling. Difference-In-difference analyses was used for evaluating policy effectiveness. Also multiple regression analyses were conducted to identify the factors associated with total medical expenditures. The control variables were demographic variables, economic status, diseases, and medical examination variables. Results: Difference-in-difference analyses showed that total average medical expenses among long-term patients has decreased by 61.85%. Of these, the hospitalization expenses have decreased by 91.63% and the drug expenses have increased by 31.85%. Multiple regression analyses results showed that total average medical expenses among long-term patients have significantly decreased by 46.5% after introducing the long-term care insurance. The hospitalization expenses have significantly decreased by 148.5%, whereas the drug expenses have increased by 53.6%. And outpatient expenses have increased by 10.4%, but the differences were not statistically significant. Conclusion: The results showed that total medical expenses and hospitalization expenses have decreased after introducing the long-term care insurance. These results could support the opinion that the health insurance spending among long-term patients will be reduced gradually by long-term care insurance through changing medical demand.