Objective This study aimed to map the geographic distribution of tertiary hospitals in Australia's most populous cities. Good access to hospital facilities improves the health and welfare of a community. The use of geographic information system (GIS) technology can assist in understanding spacial accessibility to services. Methods Using Quantum GIS, a geodatabase was constructed to incorporate hospital locations and demographic distribution data throughout Australia's 20 most populous cities. Data on the population's age groups were integrated into the geodatabase to investigate the distribution of age groups and their utilisation of access to emergency departments in tertiary public health care. Overall this study reported the geospatial distribution of 89 tertiary hospitals and the demographics of the population in areas around these hospitals. Results The majority of hospitals were located in the three most populated cities of New South Wales (NSW), Sydney, Wollongong and Newcastle, which contain a total of 32 hospitals, with 23 (72%) of the hospitals in Sydney. There were 7.8, 24.0, 53.4 and 81.0% of the population in NSW within 1.5, 3, 6 and 50 km of the hospitals, respectively. The second-highest number of hospitals was in Victoria (n = 22), with 18 (82%) hospitals located in Melbourne. This was followed by Queensland (n = 14), with eight (57%) hospitals located in Brisbane. Conclusions The results indicate that 82.2% of the Australian population lives within a 50 km radius of a tertiary hospital, with NSW having higher age distribution percentages than the other states. The results of this study could be used to locate and improve areas of need with a high burden of disease and low accessibility to healthcare services.