We studied strain-induced band splittings of ZnSe/GaAs and Zn 1-xMnxSe/GaAs epilayers of 0.064-3 μm thickness by reflectance and polarized photoluminescence. Polarized photolumi- nescence was found particularly useful in optical transition identification. The spectacular difference in magnetic field sensitivity of heavy hole and light hole exciton in ZnMnSe is also very helpful in transition identification. The evaluated heavy-light hole band splitting is in general accordance with previous data. An exceptionally strong variation of the strain with epilayer thickness is observed in the thickness range 0.5-2 μm.