Pneumonia is a common disease, and imaging is important in the diagnosis of pneumonia not only to detect the lesion but also to identify whether it is another disease. In recent years, due to the increased incidence of lung cancer, the opportunity to differentiate pneumonia from lung cancer has gradually increased. The diagnosis of the etiology and etiology of pneumonia is of great value for clinical treatment because different drugs are used for pneumonia caused by different etiologies and etiologies. Because hospitals at all levels have different abilities to examine the etiology and etiology, some hospitals are limited to treating and observing the efficacy while constantly changing antibiotics. If the morphology and distribution of pneumonia lesions can be closely integrated with the dynamic changes in imaging after treatment with medications, it will be helpful in diagnosing the cause and etiology of pneumonia. The pathology of pneumonia is the basis for diagnostic imaging. It is easier to identify alveolitis and interstitial pneumonia pathologically, but it is sometimes difficult to identify them on imaging, and it is generally helpful to identify them based on the basic morphology and distribution of the lesions. The images of alveolitis are nodules (alveoli), patches (lobules), macules (fusion of lobular lesions), lung segments, and lobe shadows. Bronchial gas images are seen within the macules, lung segments, or lobe shadows, and the lesions are distributed along the bronchial vascular bundles, with rapid dynamic changes that can occur after 1 to 2 days, and generally have more pronounced changes after 1 to 2 weeks. The images of interstitial pneumonia are small nodules (central lobular nodules), reticular, linear, and ground glass-like density lesions with blurred bronchovascular bundle margins and slower dynamic changes than those of alveolitis. However, sometimes interstitial pneumonia also presents as large, segmental or lobar shadows, such as mycoplasma pneumonia and viral pneumonia. Chest radiographs are the basic test for the diagnosis of pneumonia. Chest CT is required for differential diagnosis, especially with lung cancer. Chest X-ray is generally the best examination method to observe the dynamic changes of the lesion during treatment. In some cases, pneumonia is misdiagnosed as lung cancer based on only one chest examination (chest X-ray or CT), and radiation therapy and chemotherapy are inappropriately administered; in other cases, lung cancer is misdiagnosed as pneumonia, and the patient loses the opportunity for surgery due to excessive observation time. Although there are not many such cases, they should be taken seriously, and the interval between reviews is usually about 1 to 2 weeks, with a maximum of 4 to 6 weeks. When imaging diagnosis of pneumonia is combined with clinical aspects, it should be noted that pneumonia can have different clinical manifestations, ranging from mild to no clinical symptoms to severe to infectious shock. Some have complaints of blood in the sputum or dry cough, without fever, and the total white blood cell count may be normal. The typical clinical symptoms of pneumonia mostly refer to bacterial pneumonia. Failure to recognize the various manifestations of pneumonia can easily lead the imaging diagnosis into error. This shows that it is important for the diagnostic imaging physician to be in close contact with the clinician.