We provide an inventory of the sites and vegetation types in the Czech Republic and Slovakia that contain the highest numbers of vascular plant species in small areas of up to 625 m2. The highest numbers of species were recorded in semi-natural grasslands, in which we report four new world records for fine-scale species richness: 17 species of vascular plants in 0.0044 m2 in a mountain meadow in the Krkonoše Mts, 52 and 63 species in 0.25 and 0.5 m2, respectively, in the Kopanecké lúky meadows in the Slovak Paradise (Slovenský raj), and 109 species in 16 m2 in the Porážky meadows in the White Carpathians (Bílé Karpaty). The previous world record of 43 species in 0.1 m2 was equalled in the Čertoryje meadows in the White Carpathians, however, the previous record referred to shoot presence while the new record considers only the species rooted in the plot.We interpreted and corrected the data from the Czech Republic thatWilson et al. (2012) used to compile a list of world records and provide an updated list. The updated list contains five world records from the Czech Republic and two from Slovakia. The most species-rich grasslands and forests in the Czech Republic and Slovakia are concentrated in regions with base-rich soils in the Western Carpathians, especially in the flysch zone in SE Moravia and the Czech-Slovak borderland, and in limestone and volcanic areas in central Slovakia. The richest types of non-forest vegetation include semi-dry base-rich meadows (Bromion erecti and Cirsio-Brachypodion pinnati), base-rich pastures and mesic meadows (Cynosurion cristati and Arrhenatherion elatioris), Nardus stricta grasslands (Violion caninae and Nardo strictae-Agrostion tenuis) and some wet meadows and natural subalpine grasslands. A special type of species-rich herbaceous to open woodland vegetation develops as successional stages on gravel accumulations in Carpathian rivers after severe flooding. The maximum counts of vascular plant species in non-forest vegetation in the Czech Republic and Slovakia are 7 species/0.0009 m2, 11/0.0011 m2, 12/0.004 m2, 17/0.0044 m2, 23/0.01 m2, 37/0.04 m2, 43/0.1 m2, 52/0.25 m2, 63/0.5 m2, 82/1 m2, 88/4 m2, 109/16 m2, 116/25 m2, 131/49m2 and 133/100m2.While themaximum counts for plots smaller than 0.5m2 are from various regions and probably mainly depend on appropriate management, the maximum counts for plots larger than 0.5m2 are for two areas only, the south-eastern part of theWhite Carpathians and Kopanecké lúky meadows, suggesting the importance of regionally specific landscape processes for high species richness at such scales. Czech and Slovak forest vegetation is much poorer than grasslands, reaching maxima of 100, 109 and 118 species in plots of 100, 400 and 500 m2, which are considerably smaller than global maxima for temperate forests. Most of the species-rich sites occur on base-rich soils, in habitats with intermediate values of environmental factors, are subject to low-intensity management or natural disturbance, occur in landscapes with large areas of natural and semi-natural vegetation and probably have a long historical continuity.