Spatial and spectral characteristics of lasing from ZnxCd1−xS (0 ≦ x ≦ x 0.5), CdSexS1−x (0 ≦ x ≦ 0. 25), and CdS single crystals are investigated at temperatures 4.2, 77, and 300 K under nitrogen laser excitation. The samples are vapour‐grown platelets as well as hexagonal‐prism‐shaped “needles”. The inconsistence of the previously wide‐spread Fabry‐Perrot cavity model is shown and the interpretation is proposed in terms of a new model, namely, that of partial cavities (PC) each of them being a rectangular microbox (or microprism for “needles”). The importance of intermode scattering and optical coupling between the different PC in the process of lasing is shown experimentally.