Comparative studies of the effect of hydrogenation to concentrations of 0.33 wt% on the behavior of the creep of Zr-1wt% Nb (hereinafter Zr-1Nb) alloy in fine-grained (d(ay) =4 gm) and ultrafine-grained (d(ay) = 0.45 gm) states are performed for the creep rates in the interval 10(-7)-10(-5) s(-1) at a temperature of 673 K. Hydrogenation to concentration of 0.33 wt% is found to lead to a decrease in the steady creep rate and increase in the time to failure with simultaneous decrease in the value of deformation to failure. Possible mechanisms of deformation of the ultrafine-grained alloy under examined creep conditions are discussed. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.