Ab initio molecular geometries and vibrational frequencies of various isolated vanadate species (VO3−4, HVO2−4, H2VO−4, and V2O4−7) were calculated using different pseudopotentials. The relative merits of these were assessed by comparing the calculated molecular parameters with the corresponding values obtained from calculations at all-electron levels and, whenever available, from X-ray studies for the salts. The calculations were extended to higher oligomers (V3O5−10, V4O6−13, and V4O4−12) using the pseudopotential whose basis functions are (10s5p5d)/[2s1p1d] (55/5/5) on vanadium and (4s4p)/[2s2p] (31/31) on oxygen, which yielded the best compromise between accuracy and computational effort. The results indicate a linear centrosymmetric geometry for the isolated V2O4−7 anion. The higher oligomers have less than 180° V(SINGLE BOND)O(SINGLE BOND)V angles, except the noncyclic tetraoligomer which has a linear central V(SINGLE BOND)O(SINGLE BOND)V angle (180°). The cyclic V4O4−12 species presents a planar structure with all the vanadium and bridging oxygen atoms in the same plane. This structure was alrea dy reported for the [(CH3)CNH3][V4O12] salt. The results suggest a lower stability of the linear V4O6−13 species, in agreement with previous reports.