Pulmonary pneumocystis (PCP) is a life-threatening opportunistic infection that can occur in non-AIDS immunocompromized patients, mainly in solid organ transplant recipients, in patients with hematological malignancy and those treated for autoimmune or inflammatory diseases. In human, PCP is caused by Pneumocystis jirovecii. Over the last years, advances in cancer treatments (including new drugs, high dose and intensive chemotherapy with bone marrow or stemcell transplantation) and immunomodulation resulted in an increased number of patients with impaired immunity and risk for PCP.