Posttransplantation lymphoproliferative disorders are heterogeneous group of lymphomas. They develop as a serious complication of solid organ and haematopoietic stem cells transplantation and are associated with poor outcomes and high mortality. Even though PTLDs were considered to be a very rare complication, data from the last decade suggests that they are as not uncommon as they were previously thought to have been. When put in perspective, lymphoma make 21% of all cancers in population of solid organ transplant patients, whereas in immunocompetent patients they make for only 4% of cancers in women and 5% of cancers in men. Transplanted patients are given high doses of immunosuppression and that is the main reason for PTLD development. In conditions of immunosuppression patient’s immune system is impaired. In terms of pathogenesis, large number of PTLDs are driven by uncontrolled EBV infection, primary or reactivation, which is a consequence of inadequate immune response (no EBV specific CTLs) due to immunosuppression and which leads to malignant alteration of infected B lymphocytes. PTLDs whose development is not generated by EBV infection, but rather appear as “de novo” malignancies, are also associated with immunosuppression. PTLDs differ from lymphomas in immunocompetent patients. They have specific pathogeneses as well as predilection spots (mostly extra nodal) and they also require specific diagnostic and therapeutic approaches. The golden standard for the diagnosis of PTLD is histopathological examination and categorization based on the World Health Organization 2017 classification. Radiologic methods, mostly CT, are used to establish the stage of the lymphoma. PET-CT has proven to be highly sensitive and specific method for staging of the PTLD, but its use for staging and the assessment of the response to treatment still needs validation. Given the fact that a great deal of PTLDs are EBV driven, measurement of EBV viral loads can be used for screening of the PTLD patients for adequate prophylaxis and preemptive interventions. There are no standardized protocols for screening of the patients, but it is mostly based on identification of high risk patients and measurement of EBV viral loads. Therapeutic strategies for PTLDs include reduction of immunosuppression, surgery, radiotherapy, adoptive immunotherapy, chemotherapy, rituximab, and haematopoietic stem cell transplantation. Therapies are lymphoma specific. Search for optimal therapy that has maximal therapeutic and minimal toxic effect is still on-going.