The chemisorption of hydrocarbons (n-heptane, toluene, benzene, ethylene and cyclohexane) was studied by LEED on four different stepped crystal faces of platinum, the Pt(S)−[9(111) × (100)], Pt(S)−[6(111) × (100)], Pt(S)−[7(111) × (310)], and Pt(S)−[4(111) × (100)]. The first three surfaces exhibit thermal stability (25–1000°C) in vacuum and in the presence of hydrogen and hydrocarbons, while the last face is unstable and facets. The chemisorption of hydrocarbons produces carbonaceous deposits whose characteristics depend on the substrate structure, the type of hydrocarbon chemisorbed, the rate of adsorption and the surface temperature. Hydrocarbons on the [9(111) × (100)] and [6(111) × (100)] crystal face, form mostly ordered structures, while disordered carbonaceous layers are formed on the [7(111) × (310)] surface, which has a high concentration of kinks in the steps. The distinctly different chemisorption characteristics of these platinum surfaces can be explained by considering the interplay of four competing processes: (1) the nucleation and growth of ordered carbonaceous surface structures, (2) dehydrogenation, (3) decomposition of the organic molecules, and (4) rearrangement of the substrate (faceting). On the [9(111) × (100)] and [6(111) × (100)] crystal faces, processes (1) and (2) predominate. On the [7(111) × (310)] face, process (3) is predominant, while process (4) is the most important on the [4(111) × (100)] face. The effect of varying partial pressure of hydrogen on the chemisorption and ordering characteristics of hydrocarbons are also discussed.