We assessed the relations of visual hallucinations (VH) to cardiovascular autonomic dysfunction in patients with Parkinson's disease (PD). The subjects were 37 patients without VH (VH(−)) and 31 with VH (VH(+)). Autonomic function was evaluated on the basis of cardiac 123‐radioiodinated metaiodobenzylguanidine (¹²³I‐MIBG) uptake and hemodynamic testing with Valsalva maneuver. Systolic blood pressure (SBP) and plasma norepinephrine concentrations (NE) were measured by tilt‐table testing. ¹²³I‐MIBG uptake was lower in VH(+) than VH(−). Hemodynamic studies showed that VH(−) had only cardiac sympathetic and parasympathetic dysfunction, while VH(+) additionally had reduced vasomotor sympathetic functions. The fall in SBP during tilt‐table testing was greater in VH(+) than VH(−). NE and its difference in the supine and upright positions were decreased in VH(+). We conclude that cardiac and vasomotor sympathetic dysfunction is more severe in VH(+) than in VH(−). Severe dysfunction in PD with VH is probably attributed to Lewy‐body lesions or neuronal loss in sympathetic ganglia, the central autonomic system, or both. © 2007 Movement Disorder Society