Molecular dynamics simulations have been performed on seven aromatic polyamides to understand the structure-property relationships on their densities. The aromatic polyamides studied in this work are based on poly(hexafluoroisopropylidene) isophthalamide, HFAISO. The aim of this research is to investigate the effect of the side groups attached to the diacid monomer on the density of the aromatic polyamides. Densities were obtained via NVT and NPT molecular dynamics simulation using the COMPASS forcefield. Reliability and accuracy of the simulations were compared with the experimental density data from HFAISO and HFATERT aromatic polyamides, which are in good agreement.