Right lung atrophy and rightward shift of the mediastinum are usually caused by atrophy of the right side of the lung due to obstruction of airflow in the airway, causing the pressure in the right side of the chest to be less than that in the left side of the chest, and the mediastinum to shift to the right. After the airflow obstruction is absorbed, the affected lung atrophies and the mediastinum is shifted to the affected side. Tumors, secretions, and blood clots are the usual causes of airflow obstruction. On radiographs, the right lung is significantly reduced in size and uniformly increased in density, as well as a rightward shift of the mediastinum and elevation of the diaphragm on the right side. Usually, atelectasis is often combined with obstructive pneumonia, so antibiotics are often used in the treatment, and if it is serious, surgery is needed. When atelectasis occurs, it is important to seek medical attention and use medication or surgical treatment under the guidance of a doctor to avoid delaying the condition.