High-resolution CT of the chest is required for early lung cancer screening. High-resolution CT can detect tiny nodules in the lung, especially those around 2mm. If the small nodules grow gradually with lobar shape, short burr, pleural traction sign, pleural depression sign, etc., you need to be highly alert to the possibility of early lung cancer. Early lung cancer can also be detected by PET-CT of the chest, which can detect early lung cancer and whether metastasis occurs. Tumor markers, including carcinoembryonic antigen and squamous cell-associated antigen, can also be checked by intravenous blood sampling for early screening of lung cancer. Sputum exfoliative cytology can also be performed if the patient has blood in the sputum, which can detect the presence of metastatic cells and early tumor cells. If the nodule is large, percutaneous lung aspiration can also be performed for histocytology, which can clarify whether the nodule is early stage lung cancer.