Reflection high‐energy electron diffraction (RHEED) oscillations that continued up to three cycles were observed during metalorganic molecular‐beam epitaxial growth of CdSe on a ZnSe buffer grown on a GaAs substrate, showing two‐dimensional layer‐by‐layer growth despite the large lattice mismatch (6.85%). Based on this result, we could definitely control the growth of CdSe/ZnSe strained‐layer single quantum wells with well widths of 1–3 monolayers and of short‐period superlattices underinsituRHEED monitoring. Optical properties strongly demonstrated the successful formation of well‐defined structures consisting of these highly strained II‐VI semiconductor multilayers.