Protected Areas (PAs) are recognized as the most important core 'units' for in situ conservation. In spite of this, many studies have demonstrated that the existing PAs system often does not represent and protect the biodiversity of a region. Gap analysis methods are widely applied and documented as useful instruments to identify elements that need further protection. In this context, we introduce the concepts of potentiality of a territory using Potential Natural Vegetation mapping for conservation prioritization. A Gap analysis of Natura 2000 network in Itay was performed to evaluate the representativeness of the Potential Natural Vegetation types. In this context, the PNV map, reflecting the diversity and spatial arrangement of the natural terrestrial ecosystems, can be considered as an appropriate proxy of environmental and biogeographical diversity of Italy. The map was compiled by a panel of regional experts from throughout Italy and produced at a scale of 1:250.000. The construction of the potential vegetation map was based on existing remnants of natural ecosystem and their relation to specific abiotic site condition integrated in a hierarchical land classification approach. The adopted conservation target considered that any PNV included for less than the 10% in the Protected Area was defined as a Gap in the system. Results show that more than 32 % of PNV types recognised on the Italian territory are not protected by Natura 2000 network. The proposed PNV approach can help guiding decisions on where and how to spend scarce conservation management resources.