Mezyn National Natural Park is in the north part of the Korop District of the Chernihiv Region, 310 km2 in area, is characteristic for its strongly dismembered landscape that stipulates presence of varied localities, among them there are exterminated glaciofluvial plains, slopes and super streamside terraces. Aim of research included an expose of the value of the Mezyn NNP in maintenance of forest diversity of vascular plants and forest communities. In the Mezyn NNP there are 772 species of spontaneous flora, 194 species of the cultivated flora and 18 rarity species. The rarest species are concentrated in the centre and the east, prats of the park richer in vegetation cover. In the forest group of the Mezyn NNP 10 species of vascular plants are recordered in the Red book of the Ukraine. The wooden territory of the Mezyn NNP presents 38% and provides the variety of ecotopic terms after they provides a wide spectrum of representation and protection of forest species of vascular plants and corresponding phytocommunites.