The most productive way of expanding the range of medicinal plants is a study to prove that it is possible to use in medicine the poorly known species of plants, including obscure lungwort (Pulmonaria obscura L.). Obscure lungwort (Pulmonaria obscura L.) is a perennial herb of the Borage family (Boraginaceae) with the height of 8-30 cm, with a thick brown rhizome and numerous adventitious roots. The leaves are smoothe-edged, acuminate, hispid, sometimes with whitish spots. The flowers are on short pedicels, collected in pauciflorous, often paired cymes, sometimes collected at the top of the stem in the plate. The fruit is dry, consisting of four nutlets enclosed in a bell-shaped cup. Obscure lungwort is widespread in the regions of Central Russia. It is officinal in several countries and is used as an expectorant, emollient, astringent antihemorrhagic remedy. The article presents the developed method and gravimetric quantitative determination of the amount of polysaccharides for medicinal plant materials «Lungwort leaves». The authors also studied the stage extraction, the conditions of deposition amounts of polysaccharides.