The resistance to kanamycin of several transgenic lines of Populus×berolinensis transformed by genetic construction on the base of pBI121 binary vector and containing nptII gene was evaluated. The presence of nptII gene in the transgenic plants genomes was approved by PCR. Six transgenic lines and one control line of poplar were tested. The degrees of resistance of the studied lines of poplar to kanamycin were determined by their rooting ability. In experiments 12.5, 25, 50 and 75 mg/L of kanamycin sulphate in the growth media were tested. The results showed the different degrees of resistance of all studied poplar transgenic lines to kanamycin. The lines II and III were the most resistant and were rooted even at the highest used concentration of kanamycin in the growth media. We suppose, that differences in the resistance may be caused by different copy numbers of imported genes in the transgenic plants genomes and by differences in their expression.