PET-CT is an important imaging tool that can detect early lung cancer and whether distant metastasis has occurred. However, it belongs to the category of diagnostic imaging and has some significance in the classification of lung cancer, mainly for anatomical classification, which can distinguish between central lung cancer and peripheral lung cancer. It has no special value for cytologic classification and needs to be combined with cytologic tissue examination to further understand whether it is small cell lung cancer or non-small cell lung cancer in order to formulate different treatment plans. Therefore, PET-CT can differentiate between central lung cancer and peripheral lung cancer in anatomical classification, but it has no special diagnostic value for cytological classification and still needs to be combined with other cytological examinations to evaluate.