In presented master thesis we are dealing with problematics of delineating vacant building lands. Precise data about location and area of such plots of land are a major problem of many municipalities in Slovenia. Manually updating such spatial data demands extensive financial budget and is often time consuming. However, automatic updating is only rarely used. Presented methodology of delineating vacant building lands uses modern concepts of object-based classification to produce land cover layer and built up areas. Using GIS and spatial overlays we create potentially vacant building lands layer, which is further investigated and enhanced. As a result, we present approximated layer of vacant building lands. Presented methodology was tested on three study areas in municipality Trebnje and results were compared to vacant building lands layer created with visual interpretation and vectorisation. As results show, automated delineation of vacant building land combined with visual interpretation can achieve comparable quality as visual interpretation only.