Great Smoky Mountains National Park (GSMNP) is filled with an abundance of ecological diversity, historical significance, and recreational opportunities for visitors to explore and experience. The wide range of potential activities available in the park also present a major challenge for park visitors to plan activities that will better meet their preferences and constraints. With the large amounts of spatial and non-spatial data associated with the diverse resources and activities in the park, it is a logical choice to use geographic information systems (GIS) for storing, managing, analyzing, and visualizing the data. Nevertheless, GIS functions alone are insufficient to facilitate activity planning for park visitors. This paper presents a GIS-based spatial decision support system (SDSS) application that integrates GIS functions and SDSS designs with easy-to-use graphic user interfaces to help visitors of GSMNP choose and plan their activities more effectively to match their personal preferences and constraints. 2006 Elsevier Ltd. All rights reserved.