The first steps of the hydrogenation of a coronene molecule deposited on a graphene surface is investigated using Density Functional Theory including a van Der Waals functional. Binding energies and geometries are calculated. The role of the surface is determined by comparing hydrogenation reactions in the gas phase and on the surface. The radical product of the H with a closed-shell system is more stable on the surface. The closed-shell product of the H with a radical species is more stable in the gas phase. This can be interpreted in terms of electronic and geometrical properties of these hydrogenated species. (C) 2017 Elsevier B.V. All rights reserved.