Blue stain fungi change visual appearance of wood and supposedly do not influence mechanical properties of attacked wood. To prove or reject this hypothesis, specimens of pine wood (0.5 x 1.0 x 20.0 cm) were exposed to 2 blue stain fungi: Aureobasidium pullulans and Sclerophoma pithyophila for 2, 4, 6 or 8 weeks. Using non-destructive techniques, the following parameters were determined: mass, chemical properties (FTIR), colour of specimens, so as carbon and nitrogen content. Results showed that there are almost no chemical and mass changes: however slightly increased modulus of elasticity was determined. As expected, the colour of the specimens changed to dark tones. Furthermore, CNS analysis showed decrease of nitrogen content in colonized specimens. On the basis of these results, it can be concluded that such wood could be more extensively used for construction purposes.