Of the nine National Parks in Slovakia, Poloniny is the furthest east. It contains original extensive beech and fir-beech forest and the primeval forests of Stužica, Rožok and Havešová. Spread out across the meeting point of Slovakia, Poland and Ukraine, the park neighbours the Polish Bieszczadski and Ukrajinský Užansky national parks.
It is distinguished for the largest complex of original, and in places virgin, beech-fir woods in Europe, as well as its rare concentration of threatened animal and plant species. The area is characterised by the presence of brown bear, wolf, lynx, and catamount as well as the European wood bison.