KGaA, Weinheim. Surface plasma treatment of chitosan films is a widely used technique to control a variety of their properties, such as permeability, hemostatic activity and ability to support cell adhesion, proliferation and growth. Among other factors to be controlled, the chemical structure of initial chitosan is rarely taken into consideration. This work is aimed to highlight this factor by the example of low pressure direct-current discharge of various chitosan film samples. Contact angle measurements, X-ray photoelectron spectroscopy and scanning electron microscopy revealed differences in the film surface properties of the initial and plasma-treated films. The effect of the plasma treatment on cell viability of L929 mouse fibroblasts was studied by MTT-assay.