Various films based on cellulose, glucomannan, alone or in mixtures, were studied by solid-state NMR (ss-NMR) at 400 MHz and by time-domain NMR (TD-NMR) at three water contents (relative humidity 33, 59 and 85%). The structuring of the systems were first analyzed through the determination of the T1ρH of the polymer chains. Interactions of polymers with water were investigated through the evaluation of several spin diffusion times (THH) and relaxation time T2. The interpretation of the data and their links with the physico-chemical properties of the assemblies were achieved through complementary measurements in Dynamic Vapour Sorption (DVS) and Dynamic Mechanical Analysis (DMA).