Compared to the knowledge about the structure and function of endothelial cells of blood vessels, which was heavily developed over the past few decades, advance in the knowledge of lymphatic endothelial cells (LECs) for many years has been impossible, because of the lack of specific methods that allow histological visualization of lymphatic vessels in the tissues. The last years have brought significant progress in this field. Identification of specific markers of LECs and the development of new experimental animal models have allowed to recognize a number of antigens and growth factors of LECs and to isolate pure LECs populations. Studies indicate heterogeneity and plasticity of LECs and their active participation in the extracellular homeostasis, lipid transport, immune response and in the pathophysiology of acute and chronic inflammatory diseases, graft rejection and cancer. The article presents the current knowledge on the importance and regulation of LECs, both in health and disease.