Heat storage nanocomposites consisting of paraffin wax (PW) and multi-walled carbon nanotubes (MWNTs) have been prepared and their thermal properties have been investigated. Differential scanning calorimetric (DSC) results revealed that the melting point of a nanocomposite shifted to a lower temperature compared with the base material, with increasing the mass fraction of MWNTs, phi(w). With the addition of MWNTs, the latent heat capacity was reduced. The enhancement ratios in thermal conductivities of nanocomposites increase both in liquid state and in solid state with the increasing with phi(w) when compared to the pure PW For the composite with a mass fraction of 2.0%, the thermal conductivity enhancement ratios reach 35.0% and 40.0% in solid and in liquid states, respectively. (C) 2009 Elsevier B.V. All rights reserved.