MODELLING OF POLARIZATION PROPERTIES OF COMETARY DUST GRAINS D.A.Semenov and N.V.Voshchinnikov Astronomy Department and Sobolev Astronomical Institute, St.Petersburg University, St.Petersburg, 198504 Russia ABSTRACT Observational data for dusty comets are summarized and systemized. The dependence of the linear polarization on various parameters (the phase angle, wavelength, etc.) is analyzed. An ensemble of aligned spheroidal particles having various sizes and chemical compositions is used to fit the linear and circular polarization observed for the comet Halley.