COHERENT OPPOSITION EFFECTS FOR SEMI-INFINITE DISCRETE RANDOM MEDIUM IN THE DOUBLE-SCATTERING APPROXIMATION V.P.Tishkovets^1, P.V.Litvinov^2, M.V.Lyubchenko^3 ^1 Astronomical observatory of Kharkov National University Sumskaya St.,35, Kharkov, 61022, Ukraine E-mail: tishkovets@astron.kharkov.ua ^2 Institute of Radio Astronomy of NASU Chervonopraporna St.,4, Kharkov,61002, Ukraine E-mail: litvinov@ira.kharkov.ua Abstract The rigorous equations of the theory of multiple scattering of light by a layer of disordered medium have been used in the double-scattering approximation for semi-infinite medium to determine the influence of the particle properties on the coherent opposition effects. The effects were found to be strongly dependent on concentration of scatterers in the medium. The polarization opposition effect is more sensitive to the properties of the scatterers than the photometric opposition effect. The interference of waves could result in the negative polarization at the backscattering direction as well as in the positive polarization.