The severity of a small nodule in the lower lobe of the left lung needs to be determined by the nature of the nodule. The occurrence of small nodules in the lungs is becoming more and more common nowadays, and there are numerous causes. It is impossible to accurately determine whether a nodule in the lower lobe of the left lung is serious or not by relying only on this manifestation. Small nodules in the lower lobe of the left lung can be classified as benign or malignant. Benign nodules, such as inflammatory lung disease that may form granulomas and lead to inflammatory nodules in the lower lobe of the left lung, are usually not serious. In addition, benign lung tumors and tuberculosis may also lead to small nodules in the lower lobe of the left lung. Benign nodules usually require only close observation. However, small nodules in the lower lobe of the left lung can also be malignant lung cancer. These nodules are usually irregular in shape, have burrs at the edges, are lobulated, are more serious, and need to be surgically removed as soon as possible. If a patient develops a small nodule in the lower lobe of the left lung, there is no need to be too nervous. First of all, the nodule may be benign, and secondly, even if it is diagnosed as lung cancer, the cure rate of early lung cancer is relatively high and patients can survive for a long time after surgery. Therefore, patients should actively cooperate with the examination and treatment when nodules are found.