This study investigates the effect of cadmium exposure on the detoxification capacity in some tissues of sentinel species and edible Ruditapes decussatus (Mollusca, Bivalvia). Clams are caught and then immediately transferred to the laboratory breeding. Treatment with cadmium at 100 and 200 μg of CdCl2 per litter of water lasts 21 days. We assessed content of protein, lipid, reduced Glutathione (GSH) and malonedialdehyde (MDA) in the digestive gland, gills, adductor muscles and mantle. Results show that cadmium exposure causes in the four tissues studied an increase of lipid and protein contents, particularly evident with the highest dose. The MDA levels of the tissues studied increase significantly following treatment with a dose-response manner, while the concentration of GSH is drastically reduced in the Cd-treated clams with two doses, thus demonstrating the positive tissue sensitivity to Cd. Moreover, among the tissues studied, it appears that the mantle is the most sensitive tissue to Cd exposure and that this tissue is more suitable for monitoring metal pollution.