There are four main types of dizziness when the position changes: 1. Otoliths, otoliths are the most common type of vertigo, accounting for about half of all vertigo. Patients suddenly have a sensation of spinning in the sky for tens of seconds when they turn over on their left side, turn over on their right side, lie down while sitting down, or sit up while lying down. It is mainly due to the abnormal spinning in the sky produced by the dislodged otoliths that fall into the three semicircular canals and stimulate the peripheral nerves of the semicircular canals. This disease can be cured with a few minutes of treatment by repositioning. 2. Vestibular migraine. Patients have a youthful onset, mostly with migraine. It can be transformed into various types of vertigo as they grow older. One of them is position-related vertigo, which is also a sensation of spinning in the sky or dizziness when the patient is in a particular position. 3. Cerebrovascular disease, in some patients with cerebral infarction, especially cerebellar infarction, often have position-related vertigo. Then there is the subclavian artery steal syndrome, which is due to ischemia caused by the stenosis of the vertebral artery. The dizziness often decreases when the patient is lying down and increases when standing or walking.4. Postural hypotension, which decreases when the patient is lying down and increases when standing and walking, is mainly related to the decrease of blood pressure after the change of position. This disease has diagnostic significance when the blood pressure is measured to be lowered by more than 20 mmHg in the standing position than in the lying position.