The density functional theory (DFT) based hybrid-method B3LYP has been used to study the interaction of the nitromethane molecule (CH3NO2) with the Au(111) surface. The perfect Au(111) surface has been represented by a rather large cluster model, Au22, that was in turn used to extract information about the preferred adsorption geometry of the CH3NO2 species. In order to extract energetic information about the stability of adsorbed nitromethane, calculations were also performed for the gas-phase CH3NO2 molecule. The results obtained here are used to interpret experimental data. The computed geometry for adsorbed CH3NO2 agrees with the structure proposed from a previous experimental work.