The statistical associating fluid theory (SAFT), with monomer and dimer Lennard-Jones (LJ) reference fluids, is used to predict the phase equilibria of pure chains with different lengths. Predictions from the two versions of the theory are compared with Monte Carlo simulation results taken from the literature. We find that the additional structural information from the dimer version of the theory gives predictions in better agreement with simulation values. It is also found that the dimer version provides a much better description of the vapor pressure than the monomer one for long chains for which simulation data are available.