Objectives A generalisable simulation model is described; intended for use by managers, clinicians, planners and policy makers to understand the effects of UK waiting time targets for hospital care that have been a feature of the English NHS for some years. It is important that their development, use and emulation elsewhere is based on evidence and the model shows the effects of such targets and the actions taken to achieve them. Methods Using UK Health Episode Statistics, Patient Administration Systems and local data, the simulation model can be configured to fit the activities of many UK general hospitals. The simulations capture changes made in the hospital and their effect on waiting time performance and side effects such as cancellations. Results The paper includes a demonstration of the use of the simulation model to investigate the activity of a UK district general hospital over a two and half year period. This shows that its success in reducing patient waiting times was based on a multi-facetted approach that is much superior to individual initiatives. Conclusions Building a whole hospital model of waiting time performance is feasible and offers benefits to users in understanding the effects of changes in hospitals that are large, complex and highly congested systems. This is essential if target-based policies are to be based on evidence so that side effects can be minimised.