Experimental data for vapour liquid equilibrium for the three non-azeotropic mixtures HCFC22/CFC114 (CHClF2/C2Cl2F4), HCFC22/HCFC142b (CHClF2/C2H3ClF2) and HCFC22/HFC152a (CHClF2/C2H4F2) and vapour pressure for the pure components have been measured in pressure range up to 1.8 MPa. In a comparative study the deviations between experimental and calculated data for three correlation methods are presented. The three methods are the equations of state according to Lee-Kesler (1975) and Carnahan-Starling-de Santis (1976) and the activity coefficient model by Wilson (1964). Interaction parameters have been fitted from experimental data to the mixing rules proposed to the two equations of state and the activity coefficient parameters have been determined in the Wilson (1964) model. All three methods studied give good conformity with experimental data for the three mixtures examined.