Abstract: The hygroscopicity and thermodynamic properties of buried juvenile Pinus sylvestris L. wood with an age of 1170±40 BP were compared with the corresponding values of juvenile wood of the same species from recently cut trees. The 35ºC and 50ºC isotherms were plotted following the saturated salts method and subsequently fitted in accordance with the GAB model. The isotherms were then compared by means of the hysteresis coefficients. X-ray diffractograms were used to analyse the crystal structure of the cellulose. The effect of time on the buried wood caused hemicellulose degradation and a decrease in the crystallinity index and the crystallite length, resulting in an increase in the proportion of amorphous zones. Because of this, the equilibrium moisture contents of the buried wood are higher than in the recent wood, both in adsorption and desorption. In terms of the thermodynamic properties, the heat involved is greater in the buried wood than in the recent wood.