The paper addresses the question in the title via a survey of experienced healthcare modellers and an extensive literature review. It has two objectives.
1.
To compare the characteristics of ‘generic’ and ‘specific’ models and their success in hospitals for emergency patients

2.
To learn lessons about the design, validation and implementation of models of flows of emergency patients through acute hospitals

First the survey and some key papers lead to a proposed ‘spectrum of genericity’, consisting of four levels. We focus on two of these levels, distinguished from each other by their purpose. Secondly modelling work on the flow of emergency patient flows through and between A&E, Bed Management, Surgery, Intensive Care and Diagnostics is then reviewed. Finally the review is used to provide a much more comprehensive comparison of ‘generic’ and ‘specific’ models, distinguishing three types of genericity and identifying 24 important features of models and the associated modelling process. Many features are common across model types, but there are also important distinctions, with implications for model development.