Native and extd. woods of Populus alba L. and extd. wood of Populus deltoides x maximowiczii were hydrolyzed with CF3COOH (99%) and H2SO4 (72%) at 120 degrees C for 240 min to monosaccharides analyzed by high-performance liq. chromatog. The xylose content in CF3COOH hydrolyzates decreased with increasing the hydrolysis time (13.2% down to 5.8%) while the glucose content remained constant (34.7-49.6%). The extd. wood was better raw material for prodn. of monosaccharides.