PURPOSE: Determining the appropriate rate of radiotherapy (RT) utilization is important for health care planning and resource allocation. The difference between the observed and the appropriate RT rate is influenced by the choice of a criterion based benchmarking (CBB) or evidence-based estimates (EBEST) measure. Our primary objective was to determine the utilization of radiotherapy for cancers of the breast (B), cervix (C), lung (L), prostate (P) and rectum (R) in Alberta (AB) Canada and to compare the observed RT rates to estimates of need derived from the criterion based benchmarking (CBB) and evidence-based estimates (EBEST). MATERIALS AND METHODS: All incident cases of B,C,L,P and R cancers diagnosed in AB during 2004-8 (prior to the decentralization of provincial RT capacity) were identified from the Alberta Cancer Registry. Patients receiving RT within one year (RT-1y) of diagnosis were identified and the proportion receiving RT-1y was then calculated. Factors associated with RT utilization were analysed by region. Estimates of the need for RT were derived from CBB and EBEST methods in the literature. RESULTS: A total of n=68,164 cancer cases were identified from the ACR. RT-1y rates (95% C.I.) were B: 51.5% (50.1-52.9), C: 48.9% (43.8-54.0), L: 37.1% (35.4-38.8), P: 26.9% (25.1-28.7) and R: 39.3% (36.5-42.1). Observed rates of RT in AB were lower than estimates derived using the CBB and EBEST estimates. Shortfalls varied across cancer sites according to whether a CBB or EBEST estimate was used ranging from a low of -0.3% in cancer of the cervix to a high of 30.3% in rectal cancer. CONCLUSIONS: RT shortfalls exist in the utilization of RT in AB, Canada despite centralized cancer care and a publically funded health care system. Decisions to address shortfalls need to be mindful of how model selection can impact on findings.