Different ZnSe/GaAs epilayers prepared by low-pressure metal organic vapour-phase epitaxy under the conditions given by Nurmikko and Gunshor (1993 Physica B 185 16) are studied through their low-temperature transmission, reflection and photoluminescence spectra. Several samples are etched out from their GaAs substrate and the properties of as-grown surfaces and etched surfaces are compared. The etched samples seem to be free of in-plane strain and to behave like bulk ZnSe. The free-exciton excited state (n=2) is clearly observed in transmission, reflection and luminescence spectra. We also studied the thermal quenching of the photoluminescence in order to confirm the origin of some bound-exciton centres.