The quality of most forest sites in Sweden is classified by means of site properties, according to a system developed in the 1970's. Although its regression functions show good accuracies on country‐wide sample plot materials, the local precision in the system is shown to be low. An alternative model that utilizes digital map information is suggested, and results from a study in central Sweden are presented. Independent variables were derived from a Digital Elevation Model, a Geochemical Survey and a Quaternary Deposit Map. The site indices could be considerably better estimated forPinus sylvestriswith the map method (R2= 0.41), as compared to the existing system (R2= 0.09). ForPicea abiesthe degree of determination was equally low for the two methods.