The relation between the rotational diffusion (RD) coefficient of water molecules and viscosity, that theoretically are inversely proportional to each other, was examined by using molecular dynamics simulations. In a homogeneous bulk liquid system, both the viscosity calculated from the virial theorem and the experimental one correlated well with the inverse of water RD coefficient at various temperatures. In a heterogeneous system of water between solid walls with different solid-liquid interaction strength, the viscosity distribution was similar to the distribution of the RD coefficient inverse multiplied by density, and this suggests the possibility of extracting nanometer-scale viscosity distribution by RD. (C) 2013 Elsevier B. V. All rights reserved.