Pain in the chest when lying on the side and disappears when lying down. This situation may be the rib neuritis and rib chondritis in the chest when lying on the side after being pressed by gravity, which tends to stimulate the nerve endings and produce pain, and when the body weight returns to the original state when lying down, the pain has reduced or disappeared. At the same time, it may also be due to the presence of lung diseases, such as pleurisy or pleural effusion and other diseases, all of which tend to cause the pain to increase when the patient lies on his or her side. Therefore, the clinical appearance of chest pain when lying on the side must be checked at a regular hospital. X-rays of the chest or CT can be taken to find the specific cause and to carry out systematic and standardized treatment according to the cause so as not to delay the disease.