Physicians commonly use positron emission tomography/computed tomography (PET/CT) with fluorodeoxyglucose (FDG) to stage and monitor lung cancer. This report describes the case of a 63-year-old man with biopsy-proven lung adenocarcinoma and known brain metastases. The initial PET/CT scan at 60 min after the injection did not clearly show the intracranial lesions because of the brain’s natural uptake of the tracer. A delayed scan at 120 min markedly enhanced the lesion-to-background contrast and identified multiple FDG-avid metastatic foci. This case illustrates the clinical importance of delayed PET/CT imaging in enhancing the diagnostic precision of intracranial metastases in patients with lung cancer.