Haematological malignancies are a group of malignant neoplasms that affect the bone marrow, blood and lymphatic system and include: leukemias, non-Hodgkin's lymphomas, Hodgkin's lymphoma, myeloproliferative neoplasms, multiple myeloma, myelodysplastic syndromes and less common hematologic neoplasms. COVID-19 (from Coronavirus Disease 2019, coronavirus disease 2019) is an infectious disease caused by the SARS-CoV-2 virus belonging to the family Coronoviridae and whose pandemic was declared on March 11, 2020. It is a respiratory disease that is mostly manifested by severe respiratory distress syndrome with additional nonrespiratory symptoms. Patients with haematological malignancies have a higher risk of more severe clinical presentation of COVID-19, longer disease duration and longer hospitalizations, higher rates of admission to ICU, and higher likelihood of death. Different hematological malignancies and treatment modalities are associated with unique immune system damage and there is an interaction between haematological malignancies, the immune system, and COVID-19. According to previous studies, HM alone have a more significant effect on morbidity and mortality during COVID-19 infection compared to the presence of other comorbidities and the time interval between the last treatment of haematological malignancy and the onset of infection. Patients with HM secrete the virus for a long time and are likely to be infectious longer. Mortality is associated with discontinuation of therapy in ICUs. Patients with HM have a higher mortality rate (37-42%) of COVID-19 than the general population, with a higher risk of old age, severe infection or some advanced disease, so hospital care is justified. Patients with Hodgkin's lymphoma have slightly better outcomes. Immediate treatment of COVID-19 has primary priority over hematologic malignancies. Antiviral drugs, convalescent plasma infusion, immunomodulatory drugs, anti-inflammatory drugs and anticoagulant therapy are used in the therapy. Given that the COVID-19 pandemic continues and that vaccines for this infection exist today, vaccination along with preventive measures at all levels represent the most important measure in the fight against COVID-19 infection in patients with HM, but their effectiveness in creating immune protection remains questionable.