In this work, the Monte Carlo method of molecular simulation for a grand canonical ensemble (mu, M, and T specified) was used to simulate pure component and binary mixture adsorption of chainlike molecules in homogeneous and heterogeneous surfaces. The generated simulation data were used for the evaluation of an isotherm model. The simulations and the theoretical isotherm are based on the lattice gas model. Each surface site can be occupied by only one molecular segment. The adsorbed segments only interact with their contacting neighbors, through a characteristic potential contact energy. The studied isotherm model was adequate for describing adsorption in homogeneous solids, mainly for mixtures with low interaction energy.