The article shows relationships occurring between the age of a tree, a social class of tree position in the stand, and the volume and share of juvenile, maturing and mature wood. The object of the study were Norway spruce stands representing age classes II (from 21 to 40 years old), III (41-60 years old) and IV (61-80 years old), grown in mountain forest sites. The zones of juvenile, maturing and mature wood were determined on the basis of the proportion of late wood to early wood share in annual growth ring. Wood made inside leafy branches and within the influence of assimilation apparatus shows different structure and quality if compared with wood made of long way from the assimilation apparatus. That is why we mark juvenile and mature wood. In general juvenile wood is inseparably connection with a strong influence of assimilation apparatus, i.e. with branches of the tree. Juvenile wood is found in every tree and from the point of view of its practical application it is a disadvantageous element, limiting the possible utilization of the wood material.

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