Human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) remain associated with a high incidence of aggressive lymphomas, which represent a leading cause of morbidity and mortality in this population. Although combination antiretroviral therapy (cART) has improved survival, HIV-related lymphomas exhibit distinct biological and clinical features, often presenting at advanced stages with poor outcomes. In this context, 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has emerged as a pivotal imaging modality for diagnosis, staging, treatment monitoring, and prognostic assessment. Evidence indicates that metabolic PET parameters, such as standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG), outperform anatomical criteria in differentiating malignant from benign lymphadenopathy, distinguishing primary central nervous system lymphoma from cerebral toxoplasmosis, and quantifying tumor burden. PET/CT also improves initial staging accuracy, frequently identifying extranodal disease and leading to stage reclassification with therapeutic implications. Furthermore, baseline and interim PET findings provide prognostic information and may guide treatment adaptation, although data remain limited in HIV-positive cohorts compared to HIV-negative populations. End-of-treatment PET has shown strong prognostic value in non-HIV lymphomas and likely retains similar significance in HIV-associated cases, despite potential confounding from infection- or immune-related FDG uptake. Currently, PET/CT also informs radiotherapy planning in clinical practice, extrapolating from robust evidence in HIV-negative patients. However, prospective trials specifically addressing HIV-associated lymphomas are lacking. Interpretation remains challenging due to false positives related to immune reconstitution and concomitant infections, underscoring the need for careful clinical correlation. In conclusion, 18F-FDG PET/CT is a crucial tool in the management of HIV-related lymphomas, facilitating improved diagnostic accuracy, response assessment, and prognostic stratification. Nevertheless, prospective multicenter studies are urgently required to establish standardized PET-guided strategies tailored to this unique patient population.