A shadow on the right lung may be caused by pneumonia, tuberculosis, lung tumor and other diseases. 1. Pneumonia: when bacteria, viruses, fungi and other long-term stimulation of the lung mucosa will lead to pathogen invasion of the lung parenchyma, the patient appears to have a shadow on the right lung. 2. Tuberculosis: tuberculosis is mainly caused by Mycobacterium tuberculosis infection of the lungs, when Mycobacterium tuberculosis continues to cause certain damage to the lung tissue, it will lead to the situation that the patient has shadows on the right lung. 3. Lung tumor: the etiology of lung tumor is relatively complex, which may be caused by low immunity, infection, smoking, air pollution, ionizing radiation, heredity, improper diet and other factors. When lung tumor invades lung tissue, it can appear as a shadow on the right lung in imaging examination. There are many reasons leading to the shadows on the right lung, and it is recommended that patients go to regular hospitals in time to undergo relevant examinations, so as to clarify the causes of the disease. Once the diagnosis is confirmed, the patient should actively cooperate with the doctor to take relevant treatment measures, so as to avoid delaying the condition and damaging the health.