Abstract This paper presents first polish site of Luticola frequentissima Levkov, Metzeltin & Pavlov, with morphological and ecological characteristics. The species was found in samples collected from flowing waters and soils within the area of the Bieszczady National Park and the Magura National Park. In south-eastern Poland a low number of Luticola frequentissima cells occurred in small shaded streams. It was most frequently observed in aerophitic places (shallow and drying watercourses) and in soils. In the studied samples, apart from those cells with typical dimensions, much smaller and narrower cells with a higher number of striae were found in comparison to those in the currently available literature.