There are on-going policy concerns surrounding the difficulty in obtaining timely appointments to primary health care services and the potential impact on, for example, attendance at accident and emergency services and potential health outcomes. Using the case study of potential access to primary health care services in Wales, Geographic Information System (GIS)-based tools that permit a consideration of population-to-provider ratios over space are used to examine variations in geographical accessibility to GP surgeries offering appointment times outside of ‘core’ operating hours. Correlation analysis is used to explore the association of accessibility scores with potential demand for such services using UK Population Census data. Unlike the situation in England, there is a tendency for accessibility to those surgeries offering ‘extended’ hours of appointment times to be better for more deprived census areas in Wales. However, accessibility to surgeries offering appointments in the evening were associated with lower levels of working age population classed as ‘economically active’; i.e. those who could be targeted beneficiaries of policies geared towards ‘extended’ appointment hours provision. Such models have the potential to identify spatial mismatches of different facets of primary health care, such as ‘extended’ hours provision available at GP surgeries, and are worthy of further investigation, especially in relation to policies targeted at particular demographic groups.