Electron propagator calculations in the Partial Third Order approximation (P3) were performed on several isomers of four deoxyribonucleotide anions: deoxyriboadenosine monophosphate (dAMP-), deoxyriboguanidine monophosphate (dGMP-), deoxyribocytidine monophosphate (dCMP-), and deoxyribothymidine monophosphate (dTMP-). All calculations were performed with the GAUSSIAN-03 suite of programs. Geometry optimizations were done with the B3LYP and 6-311++G(d,p) basis. Vibrational frequencies analysis confirmed minima for all stationary points found. Major conformations of anionic mononucletides were defined in optimizations. Hydrogen bonds between phosphate oxygen and sugar or base hydrogen atoms play important roles in stabilization of the ground-state conformations. Closest minor conformations were ca. 3-4 kcal/mol higher in energy. Vertical electron detachment energies (VEDE) of all species were obtained with the P3 approximation and the 6-311++G** basis set. No restriction of the active space of orbitals was done. Existing photodetachment photoelectron spectra of four anionic mononucleotides were assigned on the basis of the P3 results. Excellent agreement with experiment was achieved. For the ground state conformer of dCMP-, the lowest VEDE may be assigned to a molecular orbital (MO) centered on the phosphate group. In the cases of dAMP- and dTMP-, both phosphate- and base-localized MOs contribute to the lowest VEDE. Only dGMP- is characterized by a very low VEDE corresponding to a base MO well separated from other final states. Predictions are also made for VEDEs and molecular orbital structures of minor conformations of anionic mononucleotides.