We report a molecular dynamics study of heat conduction in carbon nanotube (CNT)/polyethylene (PE) composites. Particular attention was focused on two key interfacial effects: the thermal boundary resistance across the CNT/PE interface, and the reduction of CNT thermal conductivity due to boundary phonon scattering at the interface with amorphous PE matrix. The calculations reveal a relatively high thermal boundary resistance across the CNT/polyethylene interfaces (similar to 1 x 10(-7) m(2) K W-1) and a moderate but non-negligible reduction (similar to 28%) of CNT thermal conductivity. By a mode-dependent phonon transport analysis, the phonon boundary scattering rate was found to increase with decreasing frequency, which suggests a size effect in the thermal conductivity reduction. Finally, the likely impact of the thermal resistances on the effective thermal conductivity of a macroscopic CNT/PE composite is quantified based on an effective medium approximation model. (C) 2013 Elsevier Ltd. All rights reserved.