[en] The spectral and kinetic properties of spontaneous and stimulated emission of radiation by CdS and CdSe platelets irradiated by picosecond pulses are investigated. A sharp increase of the delay of the stimulated luminescence from 30-40 ps to 0.6-1 ns is observed on decrease of the pumping intensity; this is attributed to the Mott transition from the electron-hole plasma to the excitons. A mechanism of indirect recombination of the electron-hole plasma involving the simultaneous emission of the LO-photon is proposed which permits one to explain the spectral position and the shape of the spontaneous and stimulated radiation bands observed