We often encounter patients with multiple primary lung cancers with ground-glass opacity. However, there are no established guidelines regarding the optimal extent of resection for multifocal lung adenocarcinoma, so it is necessary to determine the most suitable strategy for each case. A 62-year-old man visited our hospital with 7 lesions in the lung field. We evaluated the structural information using high-resolution computed tomography (HRCT) and the aggressiveness of the tumors using fluorodeoxyglucose–positron emission tomography/CT (FDG-PET/CT) and then developed a surgical strategy. Using FDG-PET/CT in addition to HRCT might improve the selection of appropriate surgical strategies for patients with multifocal lung adenocarcinoma.