We propose a 3-D crust–upper mantle seismic attenuation (Q _P ) model of the southern Apennines–Calabrian Arc subduction zone together with a 3-D velocity (V _P ) model. The Q _P model is calculated from relative t* using the spectral ratio method and the V _P from traveltime data. The final data set used for the inversion of the V _P model consists of 2400 traveltime arrivals recorded by 34 short-period stations that are part of the Italian National Seismic Network, and for the Q _P model, 2178 Pn phases recorded by a subset of 32 stations. Traveltimes and waveforms come from 272 intermediate-depth Calabrian slab events. This 3-D model of attenuation, together with the 3-D velocity model, improves our knowledge of the slab/mantle wedge structure and can be a starting point in determining the physical state of the asthenosphere (i.e., its temperature, the presence of melt and/or fluids) and its relation to volcanism found in the study area. Main features of the Q _P and V _P models show that the mantle wedge/slab, in particular, the area of highest attenuation, is located in a volume underlying the Marsili Basin. The existence and shape of this main low-Q _P (and low-V _P ) anomaly points to slab dehydration and fluid/material flow, a process that may explain the strong geochemical affinities between the subduction-related magmas from Stromboli and Vesuvius. Other interesting features in the models are strong lateral variations in Q _P and V _P that are put in relation with known important tectonic structures and volcanic centers in the area.