A dynamical polaron theory of the hydrated electron is developed. It explains experimental data on excited electron relaxation in water. The theory fairly precisely reproduces the absorbance curves for the ground and wet states of the hydrated electron as well as time dependencies of the hydrated electron formation for absorbance band at = 625 nm and at isobestic point. An analytical expression is obtained for the time required for the formation of the solvated electron from the initially delocalized state in a polar medium. It is shown that when temperature tends to zero this time logarithmically increases as temperature decreases. This result is general and for a homogeneous polar medium it does not depend on the molecular nature of a polar medium. (c) 2007 Elsevier B.V. All rights reserved.