Chitosan was characterized by Fourier transform infrared spectroscopy (FTIR), (13)C-nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and elemental analysis (EA). The thin chitosan films obtained by the casting method were heated in vacuum from room temperature to 600 degrees C. The progress of thermal degradation and carbonization process was monitored by FTIR spectroscopy in a vacuum cell, which allows the elimination of the influence of atmospheric humidity on the chitosan and carbonizate properties. The adsorption of water on the degassed chitosan and its carbonizate as well the oxidation process was also investigated by FTIR spectroscopy. The surface morphology of initial chitosan and obtained carbonaceous material was observed using atomic force microscopy (AFM). Detailed characterization of raw material and carbonization conditions is necessary for tailoring reproducible adsorbent properties.