Аннотация:The substrate conversion is considered following to the sequence: original wood – ozonized wood – holocellulose – cellulose. It is shown that ozone impact results in destruction of lignin, hemicelluloses and, partially, of cellulose. It is supposed that lignin and polysaccharides degradation in situ occurs due to reaction of molecular ozone and radical species generated in in the course of wood ozonation process.