Spatial accessibility measures are an important policy tool for managing healthcare provision and reducing health inequality. The two-step floating catchment area technique, in common with many alternative methodologies, requires that demand-side population be estimated using spatial interpolation techniques. This article studies the implications of adopting differing spatial representations of population on healthcare accessibility modeling outcomes. Results indicate that a dasymetric model yields lower accessibility scores than a standard pro rata model. More important, the difference is spatially disproportionate, suggesting that the degree of disadvantage experienced in rural areas may be greater than has previously been recognized.