The　interaction　of　dimethyl　phosphate　anion　(DMP-)　with　metal　cations　in　groups　Ia　(Li+,Na+,K+,Rb　+,Cs+),　Ib　(Cu+,Ag+,Au+),　IIa　(Be2+,Mg2+,Ca2+,Sr2+,Ba　2+)　and　IIb　(Zn2+,Cd2+,Hg2+)　were　studied　at　the　levels　of　density　functional　theory　(DFT),　Hartree-Fock　and　M　øller-Plesset　second-order　perturbation　theory　(MP2)　employing　all　electron　(AE)　and　pseudopotential　treatments.　Relativistic　effective　core　potentials　(RECP)　were　used　for　all　the　ions,　with　the　exception　of　Li　+,　Be2+.　AE　and　RECP　treatments　were　tested　for　the　Na+,K+,Cu+,Mg2+,Ca2+　and　Zn2+　complexes;　good　agreement　between　the　results　of　AE　and　RECP　suggests　that　pseudopotentials　can　also　be　used　with　confidence　for　heavy　metal　cations.　The　stabilization　energies　of　complexes　with　bivalent　ions　are　larger　than　those　with　monovalent　ones.　Therefore,　the　interaction　between　bivalent　ions　and　DMP-　is　stronger　than　that　between　monovalent　ions　and　DMP-.　In　the　same　group　they　decrease　with　the　increasing　atomic　number　of　the　metal　ions,　and　the　only　exceptions　are　the　Hg+　and　Au+　complexes.　∠OPO　and　∠COP　of　the　complexes　with　bivalent　ions　are　larger　than　those　with　monovalent　ions,　so　it　may　be　easier　for　bivalent　ions　then　monovalent　ones　bivalent　ions　to　make　polynucleotides　folded　and　winded.　The　amount　of　charge　transfer　(CT)　between　DMP~　and　bivalent　ions　is　larger　than　that　between　DMP-　and　monovalent　ions,　excepti　Cu　+　complexe　only.