A lung abscess with a smaller cavity is usually not lung cancer. Lung abscess is a suppurative inflammation of lung tissue caused by many reasons, in the early stage, it is suppurative inflammation and forms abscess after necrosis. Clinically, the cavity of lung abscess can become smaller after treatment, and active treatment is usually able to restore health. Clinically, the CT images of lung abscess and cavitary lung cancer are similar and difficult to distinguish. Usually, the doctor will carry out anti-infection treatment for 1 to 2 weeks and observe whether the lesion becomes smaller to determine whether it is a lung abscess cavity or cavitary lung cancer. If the lesion becomes smaller, it is not lung cancer, but a lung abscess due to infection. If it is impossible to judge whether it is lung abscess or lung cancer, patients are advised to go to the hospital to judge and treat under the guidance of professional doctors without delay, so as to avoid adverse consequences.