The densities of the mixtures of acetonitrile and N,N-dimethylacetamide or propylene carbonate were measured within the whole composition range of the systems at temperatures (308.15 and 318.15) K, while the isobaric heat capacity and speed of sound in these mixtures were measured within the whole composition range at 298.15 K. The results obtained were used to calculate the excess molar volume and isobaric heat capacity and the partial molar volumes and heat capacities of both components of the mixtures as well as the adiabatic (kappa(S)) and isothermal (kappa(T)) compressibility and their excess. The internal pressures of the systems were also calculated. The results have been analyzed and discussed.