This paper discusses the applicability of neutron imagingtechniques for probing the internal microstructure of several fossil woodsupon wetting and drying, two phenomena occurring in museum cabinets andendangering the fossil woods. Investigations were carried out using lignites(fossil woods) from two French localities (Rivecourt, Parisian Basin, Oise –Paleogene; Angeac, Aquitanian Basin, Charente – Cretaceous), which presentdifferent macroscopic behavior upon drying. Thanks to the highsensitivity of neutrons to hydrogen content, it was possible to track water diffusionthrough 3 mm thick samples and to follow in situ changes related to eithersupply or withdrawal of water without any special preparation and in arelevant time range (from 1 min to a few hours). Classical imageanalysis allows discriminating between the behavior of the two fossil woodswith regard to their interaction with water. Further analysis based on aFourier transform of projection images provides additional informationregarding the existence of large pores in one of the samples. Differences inpore network and internal structures have important mechanical consequencesas one of the samples retains its integrity upon drying, whereas the otherone shatters into pieces. A better understanding of the underlying processeswill clearly require multi-scale analyses, using additional techniques thatcould probe the materials at a lower scale. Such a combination of multi-scaleanalyses should provide valuable information for a better conservation ofwood remnants, which is crucial for both paleobotanical research and museumexhibits.