This paper reports on the density of solutions of polyethylene (PE) in hexane using molecular dynamics (MD) simulations based upon the accurate OPLS-AA force field at high pressures and 425 K. The NPT-MD simulations are carried out at polymer concentration 0120 wt% in hexane in the pressure range from 100 to 3000 bar. For PE solutions of 10 and 20 wt% the pressure is varied from 100 to 1000 bar. Additionally, the PE solution densities are calculated based on the modified Sanchez-Lacombe (MSL) equation of state (EOS) model to examine the accuracy of the MD computations. The simulated densities increase monotonically with increasing external pressure and compare quite favorably with the experimental and EOS data It is also revealed that the MSL EOS model produces identical mixture densities regardless of the type of the b parameter. The effect of cut-off radius to density is investigated and It is shown that the solution density increases as cut-off radius increases. A minimum cut-off radius of 1.1 nm is suggested for the intermolecular forces for accurate densities at pressures below 100 bar. for higher pressures density and non-bonded interactions display less sensitivity to cut-off distance. Analysis of the pair distribution function versus pressure is carried out where the height of the first peak increases and the radial distribution function shifts to shorter separations reflecting structural change of the condensed phase. The molecular modeling approach employed in this research provides a good insight into the polymer-polymer, polymer-solvent, and solvent-solvent interactions. The implemented methodology using the OPLS-AA force field and constant pressure/temperature algorithms compare well with the literature data, suggesting the validity of the proposed method. (C) 2014 Elsevier Ltd. All rights reserved.