Lying down chest tightness and shortness of breath can be seen in heart failure, reflux esophagitis, pleural effusion and so on. 1. Heart failure: the patient will have pulmonary stasis, affecting gas exchange, lying down due to the increase in the volume of return blood, which will lead to pulmonary stasis aggravation, can appear chest tightness and shortness of breath symptoms. 2. reflux esophagitis: it can lead to esophageal irritation, and then the symptoms of chest tightness and shortness of breath, lying down will lead to bile reflux increase, inducing chest tightness and shortness of breath attacks. 3. Pleural effusion: it will lead to the decrease of the diastolic function of the lungs and hypoxia, and when lying down due to the change of position, it can increase the compression of the lungs, which makes hypoxia aggravated and chest tightness and shortness of breath appear. Chest tightness and shortness of breath when lying down can be seen in a variety of reasons, the symptom is obvious, we should go to the hospital in a timely manner, to clarify the cause and give timely treatment.