Abstract: Accurate information on urban building types plays a crucial role for urban development, planning, and management. In this paper, we apply Object-Based Image Analysis (OBIA) methods to extract buildings from Airborne Laser Scanner (ALS) data and investigate the possibility of classifying detected buildings into ―Residential/Small Buildings‖, ―Apartment Buildings‖, and Industrial and Factory Building‖ classes by means of domain ontology and machine learning techniques. The buildings objects are classified using exclusively the information computed from the ALS data. To select the relevant features for predicting the classes of interest, the Random Forest classifier has been applied. The ontology-based classification yielded convincing results for the ―Residential/Small Buildings‖ class (F-Measure 97.7%), whereas the ―Apartment Buildings‖ and ―Industrial and Factory Buildings‖ classes achieved less accurate results (F-Measure 60% and 51%, respectively).