MODELLING OF SPECTRA OF GRB HOST GALAXIES A. Moskvitin, E.Sonbas The method of estimation of internal extinction, mass and age of host galaxies is demonstrated for three galaxies: GRB 980703, GRB 000210 and GRB 060218. The method of two-component modeling was applied: the theoretical spectrum is the sum of the spectrum of the burst component and the spectrum of the old stellar population which determines the galaxy age. Different laws of internal extinction in host galaxies were used when modeling. The MW law turned out to be the most suitable for the GRB 980703 host galaxy. In other galaxies the internal extinction turned out to be low. Thus, only from data of wide-band photometry it is possible to obtain estimations of physical parameters and probable spectral energy distributions of GRB host galaxies. The study of spectral properties of host galaxies allows us to determine the nature of GRB source progenitors.