The effect of chain architecture of graft copolymer on the structure of an adsorbed layer on a surface is investigated using an off-lattice Monte Carlo simulation method. The graft copolymers used for the simulation have the same composition but different chain architecture. The simulation results show that the layer thickness of multi-chains adsorbed onto the surface first decreases with increasing the number of side chains, indicating that the chain conformation of the adsorbed polymer becomes more flattened as the length of the side chain becomes shorter. When the length of the side chain decreases further than a critical length, however, a slight increase in layer thickness is observed, accompanied with an increase in the population of loosely bound chains. (C) 2001 Elsevier Science Ltd. All rights reserved.