Abstract: Planners use land use models to understand how cities function and to explore what cities might become. However, the development and use of such models is not unproblematic. Post-modern analyses of models highlights that they are socially constructed and that the context within which models are developed subsequently impacts their construction, use and influence. The paper uses a land use model developed by Auckland Council to examine how political actors, institutional and public politics influence the use of land models as an ‘evidence base’ for decision making. The land use model was developed as part of the council’s ‘Capacity for Growth Study’, to improve understanding of the relationships between zoning decisions, land supply and development in Auckland. The case study illustrates how models become politicised. These findings highlight the importance of PSS developers looking openly and carefully at the argument, audience and the politics within which their model will be developed and implemented, in order to facilitate the use of models for planning.