The aim of this study is to analyze how herbarium data from the National Herbarium of Ukraine could be used for conservation of rare plants. GIS-based analysis of the density of rare plant species and the level of biodiversity knowledge for the Ukrainian Polissia was performed and 11 experts were interviewed. During two time-periods (1945- 1986 and 1987-2006) rarity hotspots did not overlap. Positive correlation between species density and biodiversity knowledge was found. Factors (proximity to protected areas, cities and roads) that could encourage scientific research in a certain area were assessed. It was found that state and local large protected areas are more researched than small protected areas. Such problems as lack of botanists, insufficient number of botanical field trips, location of botanical data in different sources and lack of electronic available datasets cause gaps in biodiversity knowledge. Therefore, digitizing herbarium specimens, creation of electronic data sets and involvement of local communities into collection process should be a national priority.