The effect of the electrode potential on Surface Enhanced Raman Scattering (SERS) intensities of 2-methylpyrazine (2MP) recorded under resonant charge transfer (CT) conditions is analyzed by using a simple theoretical model [1] in which the macroscopic surface charge in the metal is modeled by several metallic clusters with different number of silver atoms (n) and charges (q), [Agn]q. Two and three linear silver atoms with zero and positive and negative charges, respectively, bounded to the 2MP through the nitrogen atom, have been taking into account.