Debates over national tobacco legislation and the use of state settlement funds demonstrate a need for information on the effects of tobacco control policies. Computer simulation models that are based on empirical evidence and that account for the variety of influences on tobacco use can be useful tools for informing policy makers. They can identify the effects of different policies, convey the importance of policy approaches to tobacco control, and help policy planners and researchers to better understand policies. This paper examines the role of simulation models in public policy, and discusses several recent models and limitations of those models.