We investigate vapor-liquid equilibria of dendrimer/solvent (benzyl ether dendrimer/toluene) systems by the combination of incompressible lattice cluster theory and atomistic simulation technique. We also examine the structure effect of dendritic polymer and the specific interaction due to the difference of interaction energies of endgroup at the periphery of dendrimer molecules. The interaction energy parameters are obtained by the pairs method including Monte Carlo simulation technique with excluded volume constraint. In the pairs method, we do not simulate the whole molecule as in molecular dynamics or molecular mechanics, but only monomer segments interacting with solvent molecules. In general, those parameters are determined by fitting experimental data. Our results show that the specific interactions between the endgroup and the solvent molecule play an important role in determining phase behaviors of the given systems.