Four cubic equations of state were used to describe thermodynamic properties of hydrogen sulfide, carbon dioxide and their mixturs in the temperature and pressure range characteristic of installations to removing gases by their absorption by aqueous solutions of alkanolamines. This region corresponds to the temperature of 300-500 K and pressure of 0,1-5 MPa Additionally, the calculations were carried out for the pressures above 5 MPa, in order to check the applicability of the equations of state to describe the processes occurring under high pressures. The compressibility factor Z was chosen as a representative factor describing thermodynamic properties of gases. The calculated values of Z and those experimentally determined elsewhere were compared. The analysis of the results allowed one to select those equations of state which could be applicable to predicting the most adequate value of the compressibility factor Z for gases under examination The Peng-Robinson equation is recommended for the region I(0,1-5 MPa) in the case of hydrogen sulfide. The Soave equation is recommended for carbon dioxide and its mixtures with hydrogen sulfide for the same region. Accuracy of prediction of the compressibility factor Z by using equations of state in the pressure range above 5 MPa is not satisfactory.