The ring-polymer molecular dynamics (RPMD) method was applied to the real-time excess electron dynamics in water clusters within a one-electron pseudo-potential model, where the excess electron motion is described with the grid-based wave function while nuclear motions of water are described with RPMD. We have simulated electronically non-adiabatic relaxation dynamics associated with s -> p excitation of an excess electron in the (H2O)(50) water anion cluster. We compared the RPMD results to the corresponding results obtained from classical MD simulations. It was found that nuclear quantum effects are playing a very important role in determining nonadiabatic relaxation time. (C) 2013 Elsevier B.V. All rights reserved.