The presence of a free hole gas and its coupling to longitudinal optical phonons were established with Raman spectroscopy in Li doped ZnSe layers grown by molecular beam epitaxy on GaAs substrates. The phonon spectra shift to higher frequencies and broaden with increasing acceptor concentration and temperature, according to the behavior of coupled phonon‐plasmon modes. Values for the concentration and mobility of the holes were obtained from the analysis of the spectral line shapes. They agree with determinations by other methods. A linear relationship was found between the spectral broadening and the hole concentration.