Up to this day 97 species of lichens were detected in the area of Třesín, which is still little explored territory from the lichenological point of view. Several of them belong to endangered (6) and vulnerable (11) species. The most valuable parts of this national nature monument can be considered fragments of older oak forests in the southern part and limestone rock formations in the northern part of the protected area. Diagrams of species diversity on di erent substrates are given. lichens, biodiversity, old-growth oak forest, Mladeč, limestone