PET-CT is the most important progress in tumor diagnosis in recent years, and it has very outstanding features in the diagnosis of many solid tumors, especially for the diagnosis of intra-pulmonary tumor lesions with an accuracy rate of more than 80%. Its main role in the diagnosis of lung cancer is reflected in two aspects, on the one hand, the determination of the nature of individual lesions in the lung and on the other hand, the determination of the presence of metastatic lesions in the whole body. Such a PET/CT examination can basically complete the clinical staging of lung cancer tumors, which is very important for guiding the selection of clinical treatment plans. Like all clinical examinations, PET/CT examination has its own clear indications. For patients who have been diagnosed with lung cancer and have undergone surgery, annual PET/CT examinations are not required if the disease is stable during regular postoperative follow-ups. If regular follow-up examinations reveal signs of tumor recurrence and metastasis, the results of PET/CT examinations need to be combined with the results of PET/CT examinations in order to clarify the nature of these abnormal lesions.