Summary: Th e aim of this study is to provide supplementary distribution records for fern species to the "Flora Atlas" of Hungarian vascular plants, published in 2015. Most of the data came from grid cells (according to the Central European Flora Mapping System) in the territory or in the surroundings of Budapest. During the work, special attention was paid to the man-made stone constructions (walls of buildings, stone fences, ruins etc.), because these objects are the most characteristic to the main study area of the survey. Th e survey resulted in new biogeographical records for 15 fern species with altogether 54 new occurrences concerning 18 grid cells. Among the species, fi ve are legally protected in Hungary: Asplenium adiantum-nigrum, A. scolopendrium, Gymnocarpium robertianum, Polystichum aculeatum and Th elypteris palustris, and further six are native members of the fl ora. Species with highest numbers of new records are Asplenium ruta-muraria (9), Asplenium trichomanes (7), Dryopteris fi lix-mas (7) and Polystichum aculeatum (7) (numbers in brackets indicate the number of grid cells from where the given species was fi rst reported). Surprisingly, four exotic fern species were also found: Adiantum capillus-veneris, Cyrtomium falcatum, Pteris cretica and Pteris cf. multifi da appearing on walls of clinker brick buildings, permanently heated during the winter period (in the present cases in old public hospitals). Based on the results manmade stone constructions, especially the older ones, seem to be suitable habitats to establish for a wide variety of ferns, including rare and protected species. Th erefore, these anthropogenic habitats deserve special attention during regional fl ora mapping projects.