Objectives: Differentiation between pulmonary tuberculoma and malignancy by preoperative diagnostic imaging sometimes proves difficult. The purpose of this study is to investigate variable manifestations of pulmonary tuberculoma mimicking lung cancer on fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) image and pathologic correlation. Patients and Methods: Twenty-five patients with a high suspicion of malignancy and histopathologically diagnosed as pulmonary tuberculoma were included. Their FDG PET/CT images, clinical data, and pathologic findings were investigated. Results: There were 18 men and seven women. The mean age was 52 +/- 8.8 years. The maximal diameter of pulmonary tuberculoma ranged from 1.7 to 4.2 cm. CT scan revealed that abnormal signs associated with malignancy such as spicular radiation, notching, and pleural indentation also frequently manifested in tuberculoma. During early imaging, positive FDG uptake was identified in 21 patients (84%), intermediate uptake in 3 patients (12%) and negative uptake in 1 patient (4%). During delayed imaging, 16 patients (64%) showed persistent elevated FDG accumulation and 8 patients (32%) experienced a slight drop of FDG accumulation. Pathologically active tuberculoma showed significantly higher FDG radioactivity during both early and delayed imaging than inactive lesion (P < 0.05). Lymphadenopathy with positive FDG uptake was identified in nine patients (36%). Conclusion: Pulmonary tuberculomas mimicking lung cancer, most of which were pathologically active lesions, commonly displayed abnormal appearances in CT scan and an increase in FDG uptake, similar to changes seen on malignancy. Coexistent lymphadenopathy made differential diagnosis even more complicated. These results suggested that positive FDG PET/CT findings should be interpreted with caution in tuberculosis-endemic regions.