The article deals with the stability of paper coated with poly-para-xylylene (parylene) as compared with the laminate paper-polyethylene that is widely used in archive paper conservation. The intensity of paper deterioration by fungi was estimated by loss in mass and by the results of electronic microscopy. The investigations showed that mould growth on paper coated with parylene (and polyethylene as well) is the result of fungi consuming the paper in parts with mechanical damage in the coating rather than the result of fungi consuming the synthetics.