The use of information systems has long been introduced in the tourism industry resulting in a number of changes in the supply and the demand chain of the tourist product. However, their potential in tourism planning and policy making has rather been neglected. Information systems to assist decision making are even less apparent in the case of managing established popular destination, which are related to a mass form of tourism development, towards a more sustainable form of development. This paper addresses these shortcomings, arguing that information systems could contribute to various aspects of sustainable tourism. A category of information systems is the Geographical Information Systems (GIS) which are capable of handling geographical data. The potential of GIS to form the base of a decision support system for policy and decision making in sustainable tourism is explored. A literature review is performed on the topic of GIS applications in tourism as well as on GIS- based decision support literature to identify the capabilities and the shortcomings. In this way, issues of designing a decision support system for sustainable tourism as well as issues of further research are highlighted.