The difference in corrosion inhibition behavior of imidazole deposited on iron by two different methods has been examined using Electrochemical Impedance Spectroscopy (EIS) and X-ray Photoelectron Spectroscopy (XPS). Adding imidazole directly into the aqueous corrosive medium has been observed to provide greater protection against corrosion, in comparison to the direct deposition of the inhibitor onto the metal surface prior to exposure to the corrosive solution. Analysis of the AC impedance spectra revealed that the value of the polarization resistance (Rp) in the case of imidazole addition to the corrosive medium was an order of magnitude higher than in the predeposited case. Results of XPS investigations suggested that in the former case, the imidazole reacts through the "pyrrole type" nitrogen with the aromatic ring more parallel to the metal surface. In the latter situation "pyridine type" nitrogen-iron interaction predominates with the imidazole ring more normal to the surface. copyright The Electrochemical Society.