Background: Positron emission tomography (PET) is often used for an indeterminate pulmonary nodule. Methods: This is a prospective study on a consecutive series of patients who had an indeterminate pulmonary nodule that was 2.5 cm or less, underwent integrated positron emission tomography using fluorodeoxyglucose-PET/computed tomographic [FDG-PET/CT] scan with the maximum standardized uptake values (maxSUVs) reported, and who underwent complete resection. Results: There were 585 patients (401 men). A total of 496 patients had a malignant nodule and the median maxSUV was 8.5 (range, 0 to 36). Eighty-nine patients had a benign nodule and the median maxSUV was 4.9 (range, 0 to 28, p < 0.001). If the maxSUV was between 0 and 2.5 there was a 24% chance the nodule was malignant, if between 2.6 and 4.0 it was 80%, and if 4.1 or greater it was 96%. False negative FDG-PET/CT was from bronchoalveolar carcinoma in 11 patients, carcinoid in 4, and renal cell in 2. False positives included fungal infections in 16 patients. Nodal involvement, whether malignant or infectious, was more likely with a pulmonary mass that had a higher maxSUV (8.4 vs 3.8 for nonmalignant lesions, 9.8 vs 4.5 for malignant lesions). Conclusions: Although integrated FDG-PET/CT is a valuable study for an indeterminate pulmonary nodule, one must be aware of causes of false positives and negatives. There is a 24% chance a suspicious nodule that has a maxSUV of 0 to 2.5 is cancer. The higher the maxSUV of the primary mass the more likely the nodes are to be involved with either malignancy or infection, and this may help direct nodal biopsy instead of pulmonary resection. © 2006 The Society of Thoracic Surgeons.