OBJECTIVES: Colorectal cancer (CRC) is the third most common cancer in the UK.  In 2007 the UK NHS introduced a CRC screening programme using the faecal occult blood test (FOBT) for biennial screening of individuals aged 60 to 69. CT colonography (CTC) is an alternative technology for CRC screening with the potential to prevent cancer by detecting pre-cancerous polyps as well as detecting cancer at an early stage. This economic analysis assessed the cost-effectiveness of CTC for CRC screening from the UK NHS perspective. METHODS: A state-transition Markov model was constructed to simulate the lifetime experience of a cohort of individuals screened under a range of scenarios using four different CRC screening technologies: FOBT, flexible sigmoidoscopy, optical colonoscopy and CTC. The model estimated lifetime costs and health outcomes;  the cost-effectiveness measure was incremental cost per Quality Adjusted Life Year (QALY).  The impact of uncertainty in underlying model parameters was evaluated in one-way and probabilistic sensitivity analyses. RESULTS: CTC screening every 10 years for individuals aged 60-69 was less expensive and yielded greater health benefits (QALYs and life years)  compared to no screening or the current UK programme of biennial FOBT screening. Compared to biennial FOBT, 10-yearly CTC screening for 60-69 year olds is estimated to avoid 661 more cases of CRC and 364 more deaths per 100,000 people invited for screening. CTC was cost-effective under a range of assumptions. The model fit to observed epidemiology data well, and was robust to changes in underlying parameter values. CONCLUSIONS: CTC has the potential to provide a cost-effective option for CRC screening and may be cost saving compared to the current programme of biennial FOBT.