This work presents in vitro studies of the functional, isolated human red blood cells (RBCs) treated with various concentrations of (NaNO2)-N-14 and (NaNO2)-N-15 with the use of resonance Raman spectroscopy (RRS) at two different laser excitations supported by absorption spectrophotometry (UV-vis). The products of the reaction between oxyhemoglobin (oxyHb) in isolated RBCs with NaNO2 were analyzed and identified in situ. The metHb-H2O was found to be the major product of this reaction; however, additional adducts were also clearly observed. Vibrational analysis allowed identification of various Hb(3+)NO(2) species (Fe3+-O-N=O with O-binding mode of nitrite ion to the Fe3+ core and nitrovinyl adducts with 2-vinyl nitration favored over 4-vinyl nitration) as well as the Fe3+-NO adduct. In addition, we were able to visualize in situ the Hb-NO2 species inside functional RBCs with the use of Raman imaging.