The results of the study elemental and group chemical composition of individual parts of the aspen bark (phloem, rhitidom) and wood are given. Bark, unlike wood, has a higher content of nutrients (N, P), micro-and macroelements, and also it is enriched with extractive substances, most of which (more than 45%) is extracted with ethanol and 1% NaOH. The number of substances extracted from wood by solvents (slightly more than 5%) is significantly lower than in the case of bark. However, in the

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... line solution wood passes a higher proportion of substances (about 15%). The outer part of the bark compared to the phloem has a higher carbon content, but a lower content of nitrogen and especially phosphorus. Nitrogen-containing compounds in the bark are mainly represented by the structural components, and phosphorus-containing compounds -phospholipids and nucleotides. The concentration of macroelements in the phloem is about two times higher than in rhytidome and exceeds 50 mol/g. In the largest amount the bark contains of magnesium, potassium and calcium, wherein the amount of the latter is more than half of the amount of inorganic elements. The main representatives of microelements (1 -5 mol /g) are zinc, iron, manganese, concentration of the others (boron, copper, cobalt, molybdenum, etc.) is very small (less than 1 mol /g). Cellulose content in the phloem and ritidome about the same or more than two times lower than in the wood. Lignin maximally accumulated in the outer part of the bark, where the concentration is over 20%. Wood is characterized by high content of acid-soluble lignin, the mass fraction exceeds 25% of the total content (18%) of the biopolymer.