In this study, the angular distribution of the annihilation gamma photons (ADAGP) and the positron lifetime in Ga2Se3 single crystals, pure and doped with Mn and Yb, were investigated. The ADAGP spectra were determined at room temperature by using a conventional long-slit spectrometer with an angular resolution of 1 mrad. The Na-22 radioactive isotope with an activity of 5 mCi was used as the positron source. Doping of the Ga2Se3 single crystals with Mn and Yb altered the parameters of the positron lifetime spectrum considerably, and the value of lifetime and the corresponding intensity of the ADAGP spectra were greatly increased. Positron trap concentrations of 1.2 x 10(18) cm(-3) for Ga2Se3 : 1 % Mn, and of 6.8 x 10(17) cm(-3) for Ga2Se3 : 1 % Yb were calculated using experimental results.