We have performed ab initio calculations in order to study the interaction of metal with the neutral ligand cytosine. The RHF and density functional as well as of MP2 and CCSD(T) correlation methods were used at 6-31+G* basis set level. The ChelpG electrostatic potential derived charge was calculated and the Mg-cytosme complex charge distribution was analyzed. MP2, B3LYP and CCSD(T) results of interaction energies show relative large values compared to the HF results. The Mg2+-o (cytosine) binding has the most stable interaction energy. Counterpoise correction was computed in order to estimate the BSSE error. (c) 2005 Elsevier B.V. All rights reserved.