Summary Magnetic resonance imaging delivers excellent, high-resolution spatial images of damp or wet wood that can supply information on internal defects of logs to optimise cutting patterns. In normal wood, the image contrast of magnetic resonance images is primarily influenced by the distribution of moisture content within the specimen. In the case of fungal attack, it is also affected by the inherent Spin-Lattice (T1) and Spin-Spin (T2) relaxation times. We investigate changes in relaxation times in beech wood (Fagus sylvatica L.) caused by fungal attack (Coniophora puteana (Schum.) Karst.) over 6 weeks. In addition, loss of compressive strength and mass loss were tested, allowing comparison to conventional methods. Magnetic resonance imaging showed superior sensitivity in detection of early stage of fungal decay in comparison to mass or strength loss assessment.