With the aim to improve volcaniclastic flows hazard zonation and risk mitigation in volcanic areas, this work presents a GIS-based study on the Sorrentina Peninsula, located southwest of the main Neapolitan volcanoes (Ischia, Procida, Campi Flegrei, and Somma-Vesuvius; Campanian Plain, Southern Italy). This area has been heavily affected by historical events with more than 200 volcaniclastic flows recorded in the last 500 years. The study here proposed combines different information, including morphometry, geology, volcanology and land use for building a susceptibility index (named VFSI) able to rank the drainage basins potentially prone to generate volcaniclastic flows. The resulting susceptibility map classifies 488 drainage basins into three different classes (low, moderate and high) over an area of about 280 km2. The proposed method allows the rapid ranking of the different drainage basins, and is propaedeutic to detailed investigation on single basins for individuating areas more prone to colluvial cover failure and associated volumes of available material for volcaniclastic flow generation.