During the field survey of small, predominantly Sphagnum-dominated mires, occupying depressions in the intensively managed landscape of the Góry Sudawskie region (NE Poland, Lithuanian Lake District), the localities of rare and threatened plant species were recorded. The most valuable of them were: Baeothryon alpinum, Carex chordorrhiza, C. pauciflora, Cinclidium stygium, Dactylorhiza baltica, D. ruthei, Eriophorum gracile, Hammarbya paludosa, Lycopodiella inundata, Oxycoccus microcarpus, Pseudocalliergon trifarium and Salix lapponum. Several red-listed species (like Carex chordorrhiza, C. limosa, Drosera rotundifolia, Epipactis palustris, Scheuchzeria palustris and Utricularia minor) were quite common and should not be considered threatened in the studied area. A striking feature was an abundant presence of species that are considered calciphilous (like E. palustris, Carex dioica and Dactylorhiza spp.). Species-rich flora of the mires is threatened first of all due to non-forest vegetation being overgrown with shrubs. It needs conservation measures (removal of shrubs). The presence of such species-rich ecosystems in highly transformed landscape is hard to explain and puts a new light on the importance of key habitats protection even in typical agricultural areas. Mechanisms protecting the mire ecosystems from external disturbances (eg eutrophication) are very important in this case and need detailed studies. The unique natural values of the studied area have remained undiscovered until now and are revealed for the first time.