In the present study, we performed the experimental study of wood structures by positron annihilation. The measurements were carried out on the positron lifetime spectrometer. The other two components are associated with the annihilation of ortho-positronium in liquids and gases filling the intra- and intercellular spaces of the wood. On the basis of experimental studies, a century old Siberian pine has been cut, the changes in the solid, liquid, and gas components of wood are dated.