Nodular shadows in the left upper lung are often indicative of lesions in the lung tissue of the left upper lung and need to be taken seriously. Clinical imaging manifestations of localized nodular shadows are common in tuberculosis, pulmonary mycosis, lung cancer and other diseases. 1. Tuberculosis: the imaging manifestations of tuberculosis are polymorphic, i.e., infiltration shadow, nodular shadow and fibrocalcified shadow can exist at the same time, with non-uniform density, which mostly occurs in the posterior apical segment of the upper lobe, the dorsal segment of the lower lobe and the posterior basal segment. 2. Lung fungal disease: the imaging manifestation is not characteristic, which can be bronchopneumonia, lobar pneumonia, single or multiple nodules. 3. Lung cancer: lung cancer may also have the manifestation of lung nodules on imaging. However, the edges of nodule shadow are rough, and there are often burrs and cut marks. The diagnosis of the disease can not be based on imaging performance alone, but requires professional doctors to evaluate and diagnose the disease according to the patient’s medical history, clinical manifestations and other examination results. It is recommended to actively seek medical attention to identify the cause of the disease and carry out targeted treatment.