Immunocompromised patients include those with innate T or B cell suppression, acquired immunodeficiency states such as those caused by human immunodeficiency virus infection, and those with medication-induced immunosuppression (chemotherapy or immunotherapy, solid organ transplant recipients). Any of these entities can place patients at increased risk of severe respiratory infection. We propose an algorithmic approach to the diagnosis of pulmonary complications that can arise in the immunocompromised patient. The first step is to gather all relevant clinical data to understand the history leading up to presentation, as well as the specific underlying immunosuppressive state. Following this, the clinician must identify the predominant imaging pattern of disease to help narrow the differential diagnosis and guide clinical management. Third, the time course of the clinical and imaging findings should be classified as acute, subacute, or chronic. We define the distinction between acute/subacute and chronic disorders as before or after 12 weeks. At the conclusion of these steps, it is hoped that a tailored differential diagnosis will allow for a rapid and precise management plan of these challenging patients.