This book reviews the interrelation between the structure and adsorption properties of water and nitrogen vapours and Ni, Cu and Ag cations of the chitosan samples modified by freeze-drying after precipitation with NaOH or Na2CO3 or drying in air, as well as cross-linking. The investigations by IR spectroscopy, X-ray diffraction and pulsed NMR show the influence of the preliminary treatments on the Supramolecular structure. The more ordered structure is observed in the freeze-dried samples of chitosan compared with the air-dried sample. The parameters of the porous structure of the chitosan samples calculated from the isotherms of water vapours adsorption and the nitrogen vapours low temperature adsorption are compared. It is revealed that the isotherms of water vapours adsorption on the chitosan samples are more sensitive to the structural modification of polymers.