Pneumonia can lead to ground-glass nodules, which are nodular, dense shadows in the lungs smaller than 3 cm. Normally the alveolar cavities are filled with air, but a variety of triggers can cause them to be filled with exudate or blood, which can lead to the discovery of ground-glass lesions on chest CT. Common causes include infectious lesions in the lungs, such as pneumonia, tuberculosis, and fungal infections. Air pollution, smoking and other factors can also lead to nodular changes in the lungs. A small number of nodules are early changes of malignant tumors in the lungs, so if you find ground-glass nodules, you need to decide on the treatment method and follow-up time according to the shape and size of the nodules.