The reaction of boron dioxide with water molecule has been studied using matrix isolation infrared spectroscopy. The boron dioxide molecules produced by codeposition of laser-evaporated boron atoms with dioxygen react spontaneously with water molecules to form OB(OH)(2), which is characterized to have a doublet ground-state with two OH groups in the cis-trans form. Isotopic substitution results indicate that the hydrolysis process proceeds via a concerted two hydrogen atom transfer mechanism. The cis-trans-OB(OH)(2) molecule is photosensitive; it decomposes to the OH center dot OB(OH) complex upon broadband UV-visible irradiation. The OH center dot OB(OH) complex is determined to have a (2)A '' ground-state with a bent C-s symmetry, in which the terminal oxygen atom of the OB (OH) fragment is hydrogen bonded with the hydroxyl radical. The OH center dot OB (OH) complex recombines to the cis-trans-OB(OH)(2) molecule upon sample annealing.