Alzheimer's disease (AD) and Parkinson's disease (PD), the two most common neurodegenerative disorders in the elderly, have been hypothesized to share genetic determinants. Recently, Li et al. proposed that a variant in the NEDD9 gene may be one of these common genetic factors. We attempted to confirm this initial observation by conducting an equivalent analysis in terms of pathologies and sample size. We genotyped the NEDD9 rs760678 SNP in three independent AD case-control studies (n = 3176) and two independent PD case-control studies (n = 1855). However, we failed to detect an association of this SNP with the risk of developing AD or PD, in any of these populations. In conclusion, these data indicate that the rs760678 SNP of the NEDD9 gene is at best a weak genetic determinant of AD or PD.