OBJECTIVES: To study the medical expenditure of insured patients with cancer and its influence factors, to analyze the utilization of pharmaceuticals, treatment-seeking behavior and the relationship between the medical expenditure and payment patterns of medical insurance. METHODS: This study involved 5351 cancer cases in 3 municipalities (Beijing, Shanghai, Chongqing) and 5 province-capital cities (Shenyang, Fuzhou, Jinan,Zhengzhou, Xining).The actual claim data of their medical expenditure and medical care utilization in 2008 were collected. Descriptive analysis and multivariate linear regression analysis were applied. RESULTS: 1) Outpatient’s annual medical expenditure per head was US$802 and inpatient’s annual medical expenditure per head was US$6200. Although the basic medical insurance (BMI) fund covered about 70% of the expenditure, the patients’ economic burden is still heavy.  2) Western medicine cost accounted for 44% to 60% of the inpatients’ medical expenditure in various cities. Cytotoxic drug usage accounted for over 80% of the anti-tumor drugs.  3) The proportion of the patients who sought outpatient and inpatient treatment in the third level hospitals was 81% and 74 %, respectively.  4) Multivariate linear regression analysis showed that the main influence factors of inpatients’ medical expenditure include medical insurance payment pattern, hospital level, category of cancer, gender, length of stay in hospital, and medical insurance type. When all factors other than payment pattern were set to be control parameters, inpatient’s annual medical expenditure per head under flat rate payment was US$348 lower than that under fee-for service. CONCLUSIONS: Medical expenditure causes heavy burden for cancer patients and the BMI fund. Flat rate payment has proved to be more effective in expenditure control compared with fee-for service. To keep the fund safe and running effectively, it is necessary to adjust present payment patterns and set rational payment standard to encourage medical care providers to control the expenditure actively.