Abstract An integrated geophysical and geological study of small mud volcanoes occurring along the external compressive margin of the chain in the northern Apennines was carried out in order to investigate the fluid pathways and the mud reservoir. Results obtained by tomographic inversion of first arrivals of 3D seismic data, and models obtained by 2D geo-electrical data, allow determination of the geometry of the buried shallow structures, and the details of the fluid seepage down to 50 m below the mud volcano surface. Seismic and geo-electrical investigations clearly detected the sub-vertical structures of the superficial outlet of the volcanic conduits and chimneys. A mud chamber was identified at a depth of 25 m. This shallow reservoir could represent the last phase of mud accumulation before final emission. Comparison with other mud volcanoes of the northern Apennines suggests a close relationship between extruded materials and substratum typology.