The structure and electron density distribution of the electronic ground state and an electronic excited state of Fe(CN)(5)(NO)(2-) in crystalline sodium nitroprusside dihydrate, Na-2[Fe(CN)(5)NO].2H(2)O, have been determined from X-ray diffraction data at 138 K. The statistically significant geometrical distortions (Delta(i) > 3 sigma(Delta(i))) of metastable state I are an elongation of the Fe-N bond by 0.049(8) Angstrom from 1.668(1) Angstrom to 1.717(8) Angstrom and a decrease in the average cis angle N-Fe-C angle by 0.8(2)degrees from 95.51(3)degrees to 94.75(19)degrees. The decrease in the angle N-Fe-C angle is understood as a minimization of ligand-ligand repulsion, which leaves the average axial to equatorial ligand distances essentially unchanged. No significant increase in bending of the FeN-O angle is observed. Analysis of the diffraction data with the multipole electron density formalism shows a significant decrease of the d(xy), electron density on the metal atom, which indicates that metastable state I (MS(I)) arises from partial depopulation of the ground-state HOMO. The results, combined with information from previously reported polarization studies, suggest that MS(I) and MS(II) are relaxed derivatives of the excited configurations a’ (2b(2))(1)a" (7e)(1) and a’ (2b(2))(1)a’ (7e)(1).