The guanidinium methanesulfonate (GMS) is a layered self-assembled organic crystal. Its structure presents a bilayer architecture and two different (0 0 1) planes can be exposed upon cleavage. In a previous paper, we have studied both planes separately and we have shown that the analysis of the rate of decay in the thermal attenuation of the He atom elastic scattered intensities allows for distinguishing between the two possible (0 0 1) cleavage planes. In this paper we investigate by means of atomic force microscopy (AFM) and He diffraction the morphology of cleaved (0 0 1) surfaces in order to study the coexistence of the two different planes on the same crystal surface. (C) 2003 Elsevier Science B.V. All rights reserved.