A summary of the results of four Polish geophysical expeditions, which constituted an extensive programme of seismic wide-angle refraction experiments in the northern Antarctic Peninsula region between 1979 and 1991, is analysed here. The results include the interpretation of 20 deep seismic sounding profiles located along the western coast of the Antarctic Peninsula. Additionally, a few shallow seismic profiles in the Deception Island area and a total of 10 reflection profiles from the Bransfield Strait and Drake Passage area were carried out. Crustal velocity models extending across the Antarctic Peninsula continental shelf between the Adelaide Island and the Bransfield Strait show a typical continental crustal structure, with crustal thicknesses of 36–42 km near the coast that decreases to 25–28 km beneath the outer continental shelf. Farther north in the Bransfield Strait region, the models document a southeastward dip of the Moho discontinuity from a depth of 12 km beneath the South Shetland Trench to 40 km under the northern tip of the Antarctic Peninsula. Beneath the trough of the Bransfield Strait, a high-velocity body with P-wave velocities exceeding 7.0 km/s was detected in a depth range of 6–32 km.