The structure, binding energies, acid vibrational frequencies have been determined for CuNO2 and AgNO2 in different coordination modes. Calculations have been performed using ab initio theoretical methods that include electron correlation and methods based on the density functional approach. Three structures are found to be stable minima on the potential energy surface : the C-2v bidentate eta(2)-O,O, a C-s monodentate eta(1)-O and the C-2v monodentate eta(1)-N structures. For both CuNO2 and AgNO2 systems the eta(2)-O,O coordination is found to be the most stable structure. The computed dissociation energies of CuNO2 and AgNO2 are 56 and 47 kcal/mol, respectively.