The thermodynamic properties of solutions of polydimethylsiloxane and silicon resin in non-polar solvents have been studied in a moderate concentration range at temperatures from 26 to 40°C. Applying Flory’s theory, the interaction parameter χ1 was calculated from the activity of solvent, which was determined from the lowering of its vapor pressure. It was found that the value of χ1 and its temperature dependency are characteristic of the interaction of polysiloxane with solvent. The heat term (ΔWs) and the entropy term (ΔWs) in χ1 were calculated from the temperature dependency of χ1 at the average temperature. It was confirmed that the obtained relation between ΔWh and ΔWs is represented by a smooth curve, independent of concentration and solvent which goes nearly through the origin.