OBJECTIVES: To assess the cost-effectiveness of introducing CT colonography (CTC) into the colorectal cancer (CRC) screening program in Japan. METHODS: A Markov model for CRC was constructed to estimate both the short-term (one-1year) and the long-term (10-year, 20-year, and lifetime) impact of CTC on costs and health outcomes using three strategies. Strategy-1 was the current screening strategy in Japan, which consists of fecal occult blood test (FOBT) and occult-colonoscopy (OC). In Strategy-2 and Strategy-3, CTC was added between FOBT and OC. In Strategy-2, those who were showed positive in FOBT were asked to take CTC (uptake=81.6%). In Strategy-3, only those who rejected OC (36.8%) were asked to take CTC (uptake=50%). ICERs for Strategy-2 and Strategy-3 against Strategy-1 were calculated. Epidemiological data was obtained mainly from statistics published by Japanese National Cancer Center. Annual discount rate for both costs and outcomes was set as 3%. One-way sensitivities analysis was performed. RESULTS: The introduction of CTC into the CRC screening program in Japan was proposed to improve the program effect. For the short-term impact, ICERs for additional CRC detection were JPY 2,202,000 (1USD=80JPY) in Strategy-2 and JPY672,000 in Strategy-3, respectively. For the long-term impact, in the base-case analysis, ICERs for additional colorectal cancer death avoided were JPY39,660,000 in Strategy-2 and JPY2,465,000 in Strategy-3, respectively. ICERs for life-year gained were JPY7,804,000 in Strategy-2 and JPY484,000 in Strategy-3, respectively. During estimating the total lifetime impact, Strategy-3 was considered more cost saving than Strategy-1. CONCLUSIONS: Although this study did not include the concept of QALY, the results suggested that CTC may be likely to improve the CRC screening program in Japan with reasonable costs. Early detection of CRC would improve patients’ quality of life; moreover, in a long-term perspective, increased costs for screening may be compensated for decreased costs when treating patients with advanced CRC.