Whether a 0.5 cm solid nodule in the left lower lung is important or not cannot be generalized, it needs to be judged according to the cause of the disease. If it is caused by benign lesions, such as pneumonia, tuberculosis, benign tumors, etc., it usually does not matter after treatment, and if it is caused by malignant tumors in the lungs, it is very important. 1. Benign lesions: when pneumonia and tuberculosis cause 0.5 cm solid nodules in the left lower lung, usually after anti-inflammatory, anti-tuberculosis and symptomatic treatments, the nodules can subside naturally with the control of the disease, and there is usually no need to be nervous. If the nodule is diagnosed as benign, regular review is usually sufficient and no special treatment is needed. 2. Malignant tumors: if diagnosed as malignant tumors, it is very important to cooperate with doctors to perform surgical resection as soon as possible, and postoperative adjuvant radiotherapy, chemotherapy and other treatments, which can improve the prognosis. When the examination result suggests a 0.5 cm solid nodule in the left lower lung, it is recommended to ask the doctor in time for further treatment under the doctor’s guidance.