Untreated and treated with oxygen under different conditions chitosan samples were used for experiments. Additional treatment was performed by (a) bubbling of air through the NaOH solution for CO2 removal and then, through slurries of chitosan in bidistilled water . Untreated or treated of chitosan was put into vessel fully filled with bidistilled water containing dissolved oxygen and hermetically plugged with an electrode sensitive to dissolved oxygen, which was registered by means of oxymeter Oxi level 2. The sorbed amounts of oxygen were evaluated according to the dissolved oxygen concentration change in water.