Spring-fed fens are unique peat-forming ecosystems, interesting not only in terms of their floral composition, but geological structure and palaeo-ecological development as well. Their existence is supported by a constant supply of groundwater rich in calcium carbonate. Geological structure is characterized by the occurrence of alternating layers of biogenic and carbonate deposits which reflect changes in moisture and temperature conditions in the fen s surrounds. Despite the low frequency of sporomorphs, in many cases pollen analysis of these biogenic deposits shed light on the changes in the plant communities before the activation of spring waters. In addition, it provided new facts for palaeo-environmental interpretations, mainly concerning climate-habitat changes. Based on the composition of pollen spectra, the examined deposits were related in most cases to the Early Holocene or the Late Glacial/Preboreal transition. The one exception here was the middle Mesoholocene age determined in the northernmost site. The results permit us not only to determine the beginning of development of these forms but also to draw climatic-stratigraphic and palaeo-environmental conclusions on a regional scale.