We have synthesized and crystallized a cytosine-decavanadate compound, Na-3[V10O28] (C4N3OH5)(3)(C4N3OH6)center dot 10H(2)O, and its crystal structure has been determined from a single-crystal X-ray diffraction. A high resolution X-ray diffraction experimental 210 K (in P (1) over bar spacegroup phase) was carried out. The data were refined using a pseudo-atom multipole model to get the electron density and the electrostatic properties of the decavanadate-cytosine complex. Static deformation density maps and Atoms in Molecules (AIM) topological analysis were used for this purpose. To get insight into the reactivity of the decavanadate anion, we have determined the atomic net charges and the molecular electrostatic potential, Special attention was paid to the hydrogen bonding occurring in the solid state between the decavanadate anion and its environment. The comparison of the experimental electronic characteristics of the decavanadate anions to those found in literature reveals that this anion is a rigid entity conserving its intrinsic properties. This is of particular importance for the future investigations of the biological activities of the decavanadate anion.