Pyroclastic density currents (PDCs) are among the most lethal volcanic phenomena and are mainly generated by column collapse, lateral blasts, or dome failure. An additional but still poorly constrained hazard is represented by PDCs produced by the collapse of hot volcaniclastic deposits. Here we investigate deposit-derived (dd) PDCs emplaced during the 1944 eruption of Vesuvius (Italy). We integrate historical literature, contemporary written and photographic sources, and new field observations with a reconstruction of the pre-eruptive topography based on vintage aerial photographs and digital elevation models. Our results show that the pre-eruptive crater geometry exerted a primary control on deposit accumulation, failure mechanisms, and runout behaviour. Volume–area relationships indicate that failure mechanisms broadly consistent with translational, near-planar collapse. Individual dd-PDCs reached volumes of up to ~3×10 6 m 3 and runout distances of ~1–1.5 km, ranking among the largest PDCs associated with sustained lava fountaining and highlighting an underestimated hazard capable of affecting areas up to 2 km from the vent.