We studied polarized photoluminescence (PL) as a function of both temperature and excitation power from m-plane CdxZn1-xO/ZnO single quantum wells having different Cd contents. The polarized PL properties at 300 K were enhanced as the Cd content increased. This enhancement is due to the anisotropic compressive strains induced within the well layers. These results are linked to the modifications of the valence band (VB) structure resulting from a change in the crystalline symmetry of CdxZn1-xO. Furthermore, there is an exception to the polarization selection rules due to excitonic localization because of a mixing of the upper VB states at low temperatures.