OBJECTIVES: Resource modelling has been largely ignored in health technology assessment (HTA) and this paper argues the need for it to be considered as a separate set of analyses to deal with the issue of implementation and feasibility. METHODS: Economic evaluation and budget impact models, which are the two economic analyses that currently feed into HTA, are briefly described before highlighting their limitations in informing issues of feasibility and implementation.  Resource modelling is defined as the quantitative assessment of technology diffusion curves, their related resource requirements and their capacity constraints