Blink reflexes (BR) to electric stimuli of the supraorbital nerve were recorded in 26 patients with dementia with Lewy bodies (DLB), 26 patients with multiple system atrophy, 26 patients with Parkinson's disease, with or without REM sleep behaviour disorder (RBD), and in 20 patients with Alzheimer's disease and 20 with progressive supranuclear palsy without RBD, and compared with recordings in 30 healthy controls. BR were significantly delayed (p<0.001) only in DLB patients in comparison with controls and with the other groups of patients; 14 (53.8%) patients had BR latency above 2 SD of the control mean, ranging from 36.1 to 46.3 ms. BR latency was not related to the presence of RBD, while a Spearman correlation rho of 0.68 was found for scores assessing the presence of cognitive fluctuations. R2 delay was prominently (71.5%) bilateral.