Patients with old tuberculosis cannot smoke. First of all, the following two points should be clear: 1. Obsolete tuberculosis means that the patient has had tuberculosis, and after treatment the tuberculosis has been controlled and cured, but the previous tuberculosis lesions will leave scars after healing, so it is called obsolete tuberculosis, and the scars will exist for life; 2. Smoking has an effect on the lungs and will increase the incidence of lung cancer. In the case of patients with old tuberculosis, it may lead to cancer of old tuberculosis lesions. Therefore, if a patient has a large lesion of old tuberculosis, he or she needs to have a regular review of chest CT to closely monitor the changes of the lung lesion and, if necessary, to have regular tests such as sputum tuberculosis bacillus examination or sputum tuberculosis bacillus culture. It is recommended that patients with old tuberculosis should develop good living habits, take appropriate physical exercise to enhance physical fitness and improve body resistance to avoid recurrence of tuberculosis, and should also pay attention to rest, strengthen nutrition, and not stay up late, smoke, or drink. Although patients with old tuberculosis are not very different from healthy people, smoking is ultimately harmful to health.