Abstract: Pericarditis is usually part of multiple systemic diseases and the first manifestation of some systemic diseases. Therefore, to find and remove the cause of systemic diseases and early intervention to delay the disease progression are helpful to prevent long-term complications and improve patient prognosis. Because it is relatively difficult to obtain pericardial effusion or pericardial tissue by pericardial biopsy, and the positive rate of biopsy is low, the identification of the cause of pericarditis is always being a difficult point. ¹⁸F-FDG PET/CT can integrate systemic physiological, metabolic, and anatomical information at one time, and has important value in determining the etiology of pericarditis. In addition, it has great advantages on determining the staging and grading of the disease, evaluating the therapeutic effect, and prognosticating, especially in the early identification of tumor recurrence, tumor restaging of the tumor, searching for the primary tumor, and positioning of the biological target area of radiotherapy. The author reviews the application value of ¹⁸F-FDG PET/CT in the diagnosis of pericarditis.