Transmission electron microscopy (TEM) measurements were carried out to investigate the ordered structures near the ZnTe/ZnSe heterointerfaces in ZnxCd1-xTe/ZnSySe1-y quantum wells. The high-resolution TEM micrographs and selective-area electron-diffraction patterns showed a CuPt-type ordered structure and a Cu3Au-type ordered structure near the ZnTe/ZnSe heterointerfaces in ZnxCd1-yTe/ZnSySe1-y quantum wells. The present results can help improve understanding for the appli cation of ZnxCd1-xTe/ZnSySe1-y quantum wells in optoelectronic devices in the blue-green spectral region. (C) 2001 Elsevier Science Ltd. All rights reserved.