Planning for sustainable cities involves supporting compact, energy-efficient urban form as well as maintaining attractive and liveable urban landscapes. Attractive cities depend highly on services provided by ecosystems, especially cultural ecosystem services (ES), which give direct benefits to urban citizens. Therefore, access to a diversity of urban functions and publicly available ES by walking and public transport should be considered when planning for sustainable cities. This could be facilitated by user-friendly planning support models. The aim of this study was to develop a GIS-based model for assessing accessibility to ES, more specifically, water-related cultural ecosystem services (WCES), via walking and public transport, with input from stakeholders. The model was applied to the Stockholm region in Sweden. Travel times and census data were used to derive measures and maps of accessibility to prioritised WCES in the region, today and in urbanisation scenarios for 2050. The results showed how access to WCES varied spatially within the region. The number of potential visitors to different WCES sites now and in the future urbanisation scenarios was estimated, and areas in need for future development of the public transport system as well as WCES were identified. The GIS-based accessibility model has potential to be used as planning support in urban planning.