Low-temperature spin relaxation time of electrons localized on iodine donors placed in the middle of a 8-nm CdTe quantum well is studied by using the photoinduced Faraday rotation technique, for donor concentrations in the range from 1 × 10 9 cm −2 to 3.6 × 10 11 cm −2. A maximum relaxation time of the order of 20 ns is found at a doping concentration near the metal-insulator transition. Adapting the theoretical description developed for bulk GaAs [R. I. Dzhioev et al., Phys. Rev. B 66, 245204 (2002)] to a quantum well, we have fitted the experimental results taking as a parameter the spin-orbit constant in CdTe. A satisfactory fit is obtained with α so = 0.079 ± 0.011, which is also very close to the calculated theoretical value. A comparison of the experimental spin relaxation times measured previously in bulk CdTe to those predicted by the theory is done. Finally, we compare the predicted spin relaxation times in bulk CdTe to those predicted in one of the most studied bulk semiconductor materials: GaAs, and in (less studied) ZnSe.