Isobaric molar heat capacities, densities and speeds of sound were determined for the dimethyl carbonate + n-octane and n-nonane systems at atmospheric pressure covering the whole composition interval and in the temperature range (288.15-308.15 K). From these data, derived properties and excess magnitudes were obtained. A strongly temperature-dependent W-shaped curves against composition were observed for excess isobaric molar heat capacities in both system, showing the other excess magnitudes regular tendencies. From these results, a comparative analysis of the existing differences between the thermodynamic behaviour of the two systems was carried out. (c) 2004 Elsevier B.V. All rights reserved.