Molecular dynamics simulations are carried out to estimate the density of average structures representative of various asphaltenes in an effort to evaluate the predictive capacities of this kind of structural models. Comparison between calculated and experimental values reveals that calculated densities are lower than experimental ones, but nevertheless calculated values show the correct tendency. This indicates that the chemical information provided by the average structures of asphaltenes is essentially correct and can be used to qualitatively estimate densities. On the basis of these results, the effect of different structural factors on calculated densities of asphaltenes was systematically studied. Large condensed aromatic rings and low hydrogen-to-carbon ratio are the main characteristics of the molecules which yield the highest densities. Also, it was found that a group-contribution method recently developed yields better density values than molecular dynamics simulations, although still lower than experimental values.