This paper reports new floristic data of 367 taxa (365 species and two hybrids) from the foothill region of Bükk Mts. ('Bükkalja', NE-Hungary) based on 5470 field collected data records. The data was collected between 1997–2014 and supplemented with herbaria (altogether 344 herbaria sheets). Data evaluation was based on the comprehensive Bükk Flora of András Vojtkó and further papers. Altogether 45 species were registered as previously unreported from the area, whereas three species had old data (Acer negundo, Elaeagnus angustifolia, Xanthium strumarium). Out of the newly registered species six native species inhabits natural habitats (Carex flacca, Ceratocephala testiculata, Glycerrhiza echinata, Gypsophila paniculata, Kochia laniflora, Marrubium vulgare), whereas five species represents the weed flora (Anthemis ruthenica, Chenopodium ficifolium, Eragrostis pilosa, Senecio vernalis, Xanthium strumarium). The majority of the newly observed species are adventives. Five species were also regarded as recent introduction regionally, although they are native in the country (mostly lowland species: Crypsis alopecuroides, Limonium gmelini subsp. hungaricum, Salsola kali, Scirpoides holoschoenus, Trifolium angulatum). Typical threats observed are landscape and habitat degradation by invasive alien species out of which 11 are newly added. Mass occurrences were detected for the following invasive alien species: Bidens frondosa, Impatiens glandulifera, Phytolacca esculenta, Xanthium italicum. 43 species are also registered, which did not have recently published data from the area. These species include more native elements representing different habitat preferences (dry grasslands, wet meadows, forest and weeds). In case of 65 species the unravelled new occurrences increased significantly, thus contributed to the clarification of their distribution pattern. It was found that the floristic data accumulated on a decade-scale are not sufficient for the analysis of floristic trends, but could serve as a good basis for surveying floristic gradients between the mountainous and lowland areas.