Photovoltaics (PV) is the fastest-growing renewable energy source at the global level and Italy has been one of the pioneers of such growth, now being one of the Countries with the largest installed PV capacity – absolute, per unit area, and per capita. In this paper we investigated the impact of PV on land use in the area with the highest density of PV farms in Italy, i.e. the Province of Lecce (Southeastern Italy): here, such impact is expected to be maximum and has been the subject of public debate. In order to map all PV farms in detail, we used participative cartography, specifically OpenStreetMap (OSM), as data source. This international project collects geographic information (often gathered by people – i.e. the so-called Volunteered Geographic Information, VGI – using widely available technologies, such as smartphone built-in GPS), in order to create freely available global topographic maps. In this paper, we used the OSM platform to create a Geographical Information System (GIS) of PV farms in the Province of Lecce. Using GIS-based techniques, we estimated land use at the municipality level and created a density map of PV farms within the study area. Using the official land cover map Corine Land Cover of 2012, we also evaluated the main changes in land use. The results highlight the correlation between spatial distribution of PV farms and geographic variables (geomorphology, demographics, tourism, etc). We also show that land take by PV farms is quite marginal even in a region such as the Province of Lecce, where the density of PV installed power is among the highest available at the global level.