Moisture absorption and diffusion, dimensional response, as well as the related stress field in materials constituting lacquer furniture were investigated to support the conservation treatment of the Mazarin Chest, renowned as one of the finest pieces of Japanese export lacquer from around 1640 preserved at the Victoria and Albert Museum in London. The measurements demonstrated that both the wood support and the lacquer adsorb considerable amounts of moisture and undergo dimensional changes which, when restrained, lead to mechanical damage. The domains of tolerable fluctuations of relative humidity (RH) are quite considerable in the mid-RH region: variations in RH in the current display environment of the chest at V&A are much smaller. The domains become, however, narrower at high RH levels. The lacquer layer, though retarding the water vapour diffusion into the wood, cannot mitigate the stress development in the object if the variations in RH become significant.