Two kinds of Pt SnO2 composite nanoceramics have been prepared using SnO2 nano particles and SnO2 agglomerate powder separately. One is of a relatively uniform and porous microstructure with a specific surface area of 8.1 m(2)/g, and the other is of a rather non-uniform microstructure with large SnO2 agglomerates and crack-like pores and a specific surface area of 6.4 m(2)/g. While the samples of uniform microstructure typically show a sensitivity of 150 to 1% H-2 - 20% O-2 - N-2 in air of 50% relative humidity (RH) at room temperature, those of non-uniform microstructure surprisingly show much higher sensitivities of 850 and 450 in air of 50% and 70% RH, respectively, to the same concentration of hydrogen. The influence of humidity on the samples has been further studied and a much higher humidity tolerance has been revealed for those samples of non-uniform microstructure. All these results demonstrate a clear and unexpected advantage of a non-uniform microstructure over a uniform one in humidity tolerance for room-temperature hydrogen-sensitive Pt SnO2 composite nanoceramics. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.