This paper describes studies on the effect of the morphology of thin solid films on the damping of quartz crystal oscillators by using gas adsorption techniques. Results indicate that rough or flat surfaces have a more significant damping effect than porous films at low coverage of gas adsorption. It is shown that the least damping occurs for adsorption onto micropores. The damping mechanism for rough surfaces is believed to be predominantly due to slippage between the adsorbed molecules and the surfaces. For porous films, the damping is consistent with a model of viscous movement in the adsorbed material. In the high coverage range, corresponding to relative pressures over 0.8, molecules adsorbed in pores with size over about a few hundred angstroms exhibit a similar damping effect to those adsorbed on rough surfaces.