The geographic position of Lebanon in the Mediterranean basin at the transition of two major landmasses, Eurasia and Africa, has contributed to its high plant biodiversity influenced by the four bio-geographical adjacent regions. Hence, this geographic area constitutes a natural laboratory for evolutionary studies. Since the integrative encompassing knowledge of the taxa is a prerequisite for appropriate management and conservation of this unique plant genetic resource, we undertook the screening of native Lebanese flora assessing its distribution according to the present land cover land use pattern. In the framework of this study, genome size assessment was used as a tool to help identifying groups with taxonomic problems. C-values were estimated by flow cytometry using the propidium iodide as intercalary fluorochrome stain. Our work is a contribution to enlarge the plant DNA-C value database by adding 250 values of Lebanese native taxa focusing on the endemic one. Our data reported the first count for 53 genus. Genome size of studied taxa ranged from 1C=0,28 pg in Hypericum thymifolium to 54.69 pg in Fritillaria alfredae. Cases of polyploidy were reported for some species usually known as diploid. The availability of these data could be profitably used in biodiversity evaluation, systematic and evolution studies because it frequently revealed the existence of important processes of speciation like polyploidy. Based on obtained data, some taxonomic groups will be suggested to be more profoundly studied.