Programed death-1 (PD-1) is an immune checkpoint pathway used by cancer cells to evade the anti-cancer activity of T cells. If this pathway is active, inhibitory signals create an unresponsive state, bringing about the tumor growth. Nowadays, the PD-1/PD-L1, L2 inhibitor therapy shows a new way of treatment to clinicians who are working with hemato-oncologic cancers. Some diseases, such as classic Hodgkin lymphoma (cHL) and primary mediastinal large-B-cell lymphoma, that express large amounts of programed death-ligand 1(PD-L1), may be a good target of such a therapy. In hematology, the anti-PD-1 therapy is used successfully and safely in cHL. Other studies are limited, or the results are not available yet. Although most of the diseases, except chronic lymphocytic leukemia and multiple myeloma, show meaningful responses, when using these drugs, we must carefully monitor autoimmune and rare, but serious side effects. In this paper, we emphasize the use of PD-1 inhibitors in hematology.