CdSe epilayers were grown on (0 0 1) InP and (0 0 1) GaAs substrates by organometallic vapor phase epitaxy, The structural and optical properties of the grown epilayers were investigated by X-ray diffraction and photoluminescence (PL). We found that the residual strain is very small in CdSe grown on GaAs and is very large in CdSe grown on InP. Moreover, the relaxation of strain is strongly anisotropic along orthogonal < 1 1 0 > crystallographic directions, with larger component of strain in the [1 1 0] direction, The asymmetric distortion of the substrate along orthogonal < 1 1 0 > directions was also found. The distortion of InP is larger than that of GaAs. We suggest that the difference between the elastic property of the InP and of GaAs substrates is partially responsible for the different residual strain in the two epilayers. The influence of residual strain on the PL properties of the two samples was also studied. (C) 2002 Elsevier Science B.V. All rights reserved.