The American College of Surgeons Oncology Group recently completed a trial evaluating the role of PET with 18F-FDG in patients with documented or suspected non-small cell lung cancer. Subjects underwent standard imaging to exclude metastatic disease before PET. Here, we report the yield of brain PET in evaluating, for potential intracranial metastases, patients who have undergone previous brain CT or MRI with negative findings. A total of 287 evaluable patients who had been registered from 22 institutions underwent whole-body 18F-FDG PET, including dedicated PET of the brain, after routine staging procedures had found no suggestion of metastatic disease. Patients were followed postoperatively for disease-free and overall survival, with a minimum follow-up of 6 mo. Patients with specific brain abnormalities identified by PET were further examined, and the findings were evaluated along with the results of CT and MRI, clinical management, and follow-up. In 4 patients, PET found focal 18F-FDG uptake in the brain suggestive of metastatic disease; however, metastatic disease was excluded clinically in all 4 by negative findings on further brain imaging. All 4 patients remained alive at follow-up (mean duration, 10.5 mo; range, 6-16 mo). In patients with suspected or proven non-small cell lung cancer considered resectable by standard imaging, including routine preoperative contrast-enhanced CT or MRI of the brain, PET of the brain provides no additional information regarding metastatic disease.