The self-similarity conjecture can provide an assessment of regionalisation procedures for flood frequency analysis if the scaling properties of flood flows as parametrised by drainage area are considered. This approach is developed to investigate whether simple scaling can be used to discriminate among different flood probabilities in relatively small regions with high variability of climate and geomorphological features. Detailed simulations for a small basin in Thyrrhenian Liguria (North-West Italy) show self-similarity or simple scaling to properly represent the spatial variability of flood probabilities. The scaling properties of annual flood series for North-West Italy are also investigated. Although flood statistics display multiscaling when considering North-West Italy as an individual homogeneous region, one can classify geographically consistent regions in this area where self-similarity cannot be rejected. Accordingly, the index flood procedure can be properly applied to these regions in order to estimate flood probabilities in ungauged catchments, and the scaling exponent of flood probabilities resulting from both basin simulations and frequency analysis of annual series for the region including this basin.