Lung cancer can be diagnosed by imaging examination, sputum cytology examination, fiberoptic bronchoscopy and excisional biopsy. 1. Imaging examination: for most lung cancer patients, abnormalities can be found by using CT examination of lungs, which often manifests as lung masses or nodules, with enlarged lymph nodes under mediastinal window in the vicinity of paratracheal, hilar and ronchi. Under the guidance of CT, puncture biopsy and pathologic examination of lung lesions can be done to diagnose whether it is lung cancer. 2. Sputum cytology examination: many lung cancer patients will cough up a small amount of sputum in the early stage, and cancer cells can be detected in the sputum of lung cancer patients. Therefore, sputum cytology is the easiest way to diagnose early lung cancer. 3. Fiberoptic bronchoscopy: it is mainly used to observe the pathological changes of bronchial lining and lumen with the help of instruments. Through the examination, the location, size and shape of lesions in the lungs can be visualized. If any abnormality is found, some tissues different from human body can be taken directly for laboratory tests. 3. Pathological biopsy: Tumor tissues can be obtained through lung puncture, and finally through pathological examination to determine whether it is a tumor or not and further clarify the type of tumor. To sum up, the diagnosis of lung cancer needs to be combined with various examination methods. Some diagnosed lung cancer patients also need to undergo systemic examination to clarify whether there is metastasis. It is recommended that patients should go to regular hospitals in time for clear diagnosis and early treatment.