Several inflammatory conditions affect the chest, and the inflammation they cause can be detected by FDG-PET/CT scans (Table 1). These conditions include granulomatous infections, giant cell arteritis, fibrosing mediastinitis, IgG4-related disease (formerly autoimmune pancreatitis), organizing pneumonia, granulomatosis with polyangiitis, and histiocytic processes (eg, Erdheim-Chester disease). These conditions are commonly thought of as pitfalls, referring to real pathology that can mimic the appearance of cancer on FDG-PET scans, and are known for leading to inaccurate interpretations and subsequent inappropriate interventions. On occasion, one has the pleasure of accurately pinpointing one of these conditions based on the PET/CT imaging alone (Table 1). Diagnosing inflammatory conditions is often a result of careful comparison with prior imaging, and the systemic pattern of activity (Fig 2). Knowledge of suggestive patterns of activity seen with inflammatory diseases such as IgG4-related disease, granulomatosis with polyangiitis (Wegener), or sarcoidosis is critical. Perhaps the major impact of FDG PET/CT scanning for patients with these conditions is not the diagnosis, but the posttherapy follow-up.