Sitting without chest tightness lying down chest tightness, consider with coronary heart disease, cardiac insufficiency, gastroesophageal reflux, respiratory diseases related to the need for further examination to clarify the cause. 1. Coronary heart disease, cardiac insufficiency: after lying down, the amount of blood returning to the heart increases, resulting in an overburdened heart, cardiac muscle contraction, diastolic weakness, which can cause chest tightness, breathlessness symptoms. Symptoms can be relieved or alleviated when sitting. 2. Gastroesophageal reflux: When lying down in the horizontal position, the reflux of stomach contents stimulates the esophagus and throat spasm, which can also cause symptoms of chest tightness. It can be accompanied by burning discomfort in the chest. 3. Respiratory diseases: such as chronic obstructive pulmonary disease, serious lung infections and other diseases, can appear lying down chest tightness obvious performance, can be accompanied by coughing, coughing up sputum. Sitting without chest tightness lying down chest tightness, to pay enough attention to timely medical care, clear cause of the active treatment, in order to avoid delays in the condition.