Abstract Syncope associated to orthostatic hypotension (OH), urinary incontinence and constipation is common symptoms in demented patients, mainly in dementia with Lewy bodies (DLB) and in Parkinson's disease dementia (PDD). Alzheimer's disease (AD) and fronto temporal lobar degeneration (FTLD) show less autonomic dysfunction. Urinary symptoms are a prominent component of normal pressure hydrocephalus (NPH). There are non invasive tests including standard cardiovascular tests, 123 I-metaiodobenzylguanide (MIBG) cardiac scintigraphy, urodynamic tests, gastrointestinal motility studies, sweating reflexes and pupillary responses that assess autonomic dysfunction in these patients. The study of autonomic symptoms and abnormal tests in patients with dementia is useful to prevent morbidity due falls, severe constipation and to avoid side effects of drugs that interfere with autonomic function.