We performed an ab initio mol. dynamics simulation of the paramagnetic transition metal ion Cr3+ in aq. soln. Isotropic hyperfine coupling consts. between the electron spin of the chromium ion and nuclear spins of all water mols. have been detd. for instantaneous snapshots extd. from the trajectory. The coupling const. of first sphere oxygen, Aiso(17OI)=1.9±0.3 MHz, is independent on Cr-OI distance but increases with the tilt angle for the water mol. approaching 180°. First sphere hydrogen spins have Aiso(1 HI)=2.1±0.2 MHz which decreases with increasing tilt angle and shows a Cr-HI distance dependence. The hyperfine coupling consts. for second sphere 17O is neg. and an order of magnitude smaller (-0.20±0.02 MHz) compared to first sphere.