This article gives the reader an overview of NMR and MRI of fluids in wood. It does not cover solid-state NMR methods, such as CP MAS, that give chemically resolved information about solid wood macromolecules. The most important fluid naturally existing in wood is water, and the article provides an overview of the relaxation spectrum of water components. NMR and MRI methods used for determining the moisture content and distribution are also reviewed. NMR of fluids absorbed in wood or flowing through wood provide detailed information about the microstructure of wood, and the article summarizes wood structure characterization by means of pulsed-field gradient spin-echo NMR (PGSE NMR), NMR cryoporometry, and remote detection MRI of fluids.