Abstract The Alpine Marmot (Marmota marmota marmota) is widespread all over the eastern side of Como's province (NW Italy), with the exception of the Grigne massif, Mount Resegone and Mount Due Mani. These are three geographically isolated mountain ranges. For this reason the Faunal Service of the Provincial Administration of Como has undertaken a project aimed at releasing individuals in the Grigne area. In this early stage a suitability analysis was performed, using a Geographical Information System (GIS). Field data were collected concerning colonies distribution and spatial structure, inside a sample area where stable populations are present. This area is quite similar to the release area, and covers the whole part of Prealpi Comasche between Sponda Biandino and the Artavaggio plains. Using GIS data analysis techniques a base thematic cartography was set up, which was based on informational strata such as altitude. slope and aspect. This information helped us to calculate optimum values of environmental ranges to look for within the release area. Finally, GIS siting operations highlighted zones suitable for releasing marmots. The use of a GIS instrument helped in the definition of colonisation-suitable sites on the basis of several parameters, optimising the costs-benefits ratio with the further advantage of being able to keep the topographical database up to date.