CT can be used as an important basis for diagnosing lung cancer in early stage, besides CT, pathology, bone scan and other tests are also important. CT is an important way to assist in the diagnosis of lung cancer as well as its staging. Through CT, the size of the lesion, whether there is lymph node metastasis and distant organ metastasis can be evaluated, so it can guide the staging. Pathologic examination is the gold standard to confirm the diagnosis, so the diagnosis of lung cancer needs the final pathologic results, and the pathologic results after surgery can also help to guide a more accurate staging. Bone scan is able to assess whether there is bone metastasis, and is also an important basis to negate early lung cancer. Those with localized pain and elevated blood calcium should undergo bone scan to exclude metastasis.