A high-resolution CT scan of the chest can examine the chest wall, lungs, and mediastinum. 1. Chest wall: asbestosis, pleural thickening and pleural effusion that cannot be shown on chest radiographs can be found. If small pleural nodules or masses are found, it helps in the diagnosis of metastasis and mesothelioma. According to the CT value of pleural masses, it can identify encapsulated pleural effusion. The diagnosis of hemangioma of the chest wall can be confirmed by enhanced CT; it can show rib fractures and rib destruction very well. 2. Lung: it is valuable in the early diagnosis of peripheral lung cancer: it helps in the diagnosis of central lung cancer when stenosis or truncation of the main bronchus, lobar bronchus, and segmental bronchus are found; high-resolution CT (HRCT) may show diffuse interstitial spaces that cannot be visualized on chest radiographs. Qualitative lesions are useful for early diagnosis and differential diagnosis; they may also reveal pulmonary blisters, bronchiectasis, and small tuberculous cavities that cannot be visualized on chest radiographs. 3. Mediastinum: it can find the enlarged lymph nodes that cannot be found on chest film, and according to the CT value and location of the mass, it can help the qualitative diagnosis of mediastinal mass; it can also be used to distinguish fatty, cystic and solid masses. It can also be used to distinguish fatty, cystic and solid masses, and enhancement scan can diagnose pulmonary aneurysm and aortic aneurysm.