OBJECTIVES: To estimate trends in medical Computed Tomography (CT) use and associated radiation exposure in Canada, we assessed the annual effective dose from CT scans, and estimated the potential related cancer risk. METHODS: CT examinations in Canada have increased over 400% since 1994 to approximately 4.4M scans annually in 2010. Despite the medical benefits, there is concern regarding radiation-related cancer risk. We developed a mathematical model to estimate the annual effective dose, and potential cancer risk in Canada from CT , by year, age, sex, and type of CT exams. RESULTS: From 1994 to 2010, CT examinations increased from 38 to 127 per 1,000 population (7.8% annual increase). Abdominal / pelvic CT had the largest annual increase at 10.3%, a five-fold increase in scans, whereas brain and spine scans grew two-fold. The average effective dose per  CT scan went up from 6.1 mSv to 7.1 mSv. The mean per capita effective dose increased four-fold, at 8.5% annually, from 0.23 mSv to 0.90 mSv. In 2010, males and females ages 65+, had annual doses of 3.2 mSv and 2.5 mSv per capita, respectively. In the base-case scenario, the potential incidence of radiation induced cancer was estimated at 2.9 cases per 10,000 population.  Extensive sensitivity analyses have been performed. The risk of cancer in males 65+ was 2.9 times greater than for males 40-64. The risk in females 65+ was 2.2 times greater than for females 40-64. The risk in males 65+ was 29% higher than in females 65+. CONCLUSIONS: For many patients, the potential benefits of CT scans outweigh foreseeable carcinogenic risk. Substantial increases in CT technology utilization and recent studies linking low-dose ionizing radiation to cancer suggest it would be sound policy to lower patient exposure to ionizing radiation and informing patients about the potential risk.