The diagnosis of pulmonary isolation disease currently relies on imaging. Cystic masses or smooth-edged mass-like shadows in the posterior basal segment of the lower lobe adjacent to the diaphragm and cardiac shadow should be considered as a possibility of this disease. There is no significant specificity of pulmonary isolation disease in routine chest x-ray. It mostly presents with recurrent lung infections, rounded soft tissue masses in the lower lungs, decreased density in the adjacent lung fields, or as lung abscesses, abscess chests, bronchopleural fistulas, or bronchiectasis. Sometimes it may appear as an air-containing cyst, or as a solid shadow in the lower lung with a liquid-gas plane. Therefore, chest X-ray only suggests the possibility of pulmonary isolation disease for further examination. CT examination: using plain and enhanced scans Pulmonary segregation is manifested in a variety of forms on CT examination, such as cystic thin-walled cavities with smooth margins, or solid masses with uniform density, or cystic solid lesions. The solid portion has a soft tissue density on CT and the lesion is mostly one lung segment in extent or larger with emphysema around the lesion.CT plain scan sometimes reveals vascular branches from the aorta in a banded image. Enhanced scans also show increased restrictive vascularity at the lesion site, making it easy to detect blood supply vessels. CT scan of the chest is extremely valuable in assisting the clinical diagnosis of pulmonary isolation, mainly because: 1) its cross-sectional scan helps to show the abnormal blood supply arteries, and this sign has qualitative diagnostic value; 2) its high resolution helps to clearly show the fine structures in the isolated lung; 3) the CT examination method is painless, non-hazardous and widely used. Therefore, CT examination has considerable value in the diagnosis of pulmonary isolation disease. However, because most of the abnormal arteries are within or parallel to the pulmonary ligament and their density is similar to that of soft tissue, it is difficult to identify them by CT plain examination. In addition, some anomalous vessels come from the diaphragmatic artery, abdominal aorta, intercostal artery, etc., and coupled with the limitations of CT plain scan examination, it will not be able to include all these anomalous vessels, and its preoperative anomalous vessel clarification rate is very low. Enhanced CT examination of the chest not only shows the morphological characteristics of the lesion and the surrounding lesions, but also easily shows the abnormal blood supply arteries, thus greatly improving the correctness of diagnosis, and is the gold standard for the diagnosis of pulmonary isolation disease by CT examination. In addition, MRI is a non-invasive, convenient and easy-to-use imaging examination that does not require contrast enhancement, and has the advantages of vascular flow-space effect and multi-planar and multi-angle observation, so it can better display the internal structure of the lesion, blood supply arteries, drainage veins and their direction. At the same time, three-dimensional reconstruction imaging can be performed to further understand the adjacent relationship and provide anatomical information for surgical treatment. When a mass in the posterior basal segment of the lower lobe is found and does not absorb for a long time, pulmonary isolation disease should be suspected. In addition to routine CT examinations, other imaging methods should be used, especially performing enhanced CT, MRI or 3D reconstruction examinations, in an effort to clarify the location of the abnormal blood supplying arteries preoperatively.