[1] In French Polynesia, the young (< 5Ma) Society Islands appear to result from intraplate volcanism, while the old (>50 Ma) Tuamotu plateau was likely created at or near the ridge axis. The structure of the crust between those two archipelagoes is constrained by a 300 km long refraction seismic profile. Crustal and upper mantle arrivals recorded by 6 OBHs and 3 land stations were used to provide a 2D model of the crust. Results of our study, combined with that of Grevemeyer et al. [2001] show a slight flexure below the Tahiti apron, while a deep crustal root (21 km) underlies the Tuamotu plateau. These structures reflect the different modes of load emplacement and compensation mechanisms between these two volcanic edifices, consistent with an increasing elastic thickness of the oceanic lithosphere with age.