A hybrid ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulation has been performed to evaluate hydration structure and dynamics of the Cd2+ ion in aqueous solution. Two hydration shells were identified at the mean distances of 2.3 and 4.8 Angstrom, with coordination numbers of 6 and similar to12, respectively, which is in good agreement with X-ray data. Librational and vibrational spectra of the hydrated Cd2+ ion have been evaluated, showing a fairly complex spectrum for Cd-O vibrations, whose stretching force constant of 68 N m(-1) is slightly higher than that for Hg-O vibrations. The mean residence time for the 2nd shell ligands was determined as 10 ps, and the calculated hydration energy of -458 kcal/mol is close to the experimental value of -438 kcal/mol.