Introduction the: GBA -N370S mutation is one of the most frequent risk factors for dementia with Lewy bodies (DLB) and Parkinson's disease (PD). We looked for genetic variations that contribute to the outcome in N370S-carriers, whether PD or DLB., Methods: Whole-genome sequencing of 95 Ashkenazi-N370S-carriers affected with either DLB (n = 19) or PD (n = 76) was performed, and 564 genes related to dementia and PD analyzed., Results: We identified enrichment of linked alleles in PINK1 locus in DLB patients (false discovery rate P = .0412). Haplotype analysis delineated 1.8 Mb interval encompassing 29 genes and 87 unique variants, of them, KIF17 -R869C received the highest functional prediction score (Combined Annotation Dependent Depletion = 34). Its frequency was significantly higher in 26 DLB-N370S-carriers compared to 140 PD-N370S-carriers (odds ratio [OR] = 33.4 P = .001, and OR = 70.2 when only heterozygotes were included)., Discussion: Because KIF17 was shown to be important for learning and memory in mice, our data further suggest, for the first time, its involvement in DLB, and possibly in human dementia., Competing Interests: O.G., M.G.W., T.S., R.A., Y.M., and A.B.S. declare no conflicts of interest. Y.Y.W. is an employee of NRGene Ltd. A.T. has received honoraria from AbbVie Inc. and research grants from the Michael J. Fox Foundation. T.G. reports advisory board membership with honoraria to her and to her institution from AbbVie Israel, Neuroderm Ltd., and Allergan; research support from Phonetica Ltd., Israeli Innovation Authority, Sagol School of Neuroscience (Brain Boost), and the Parkinson's Foundation; and travel support for herself and her team from Abbvie, Allergan, Medisson, Medronic. A.M. has received consulting fees from NeuroDerm and research grants from the Michael J. Fox Foundation, the Israeli Science Foundation, and the US Department of Defense. N.G. serves as a consultant to Intec Pharma, NeuroDerm, Denali, Abbvie, Sanofi‐Genzyme, Biogen, Vibrant, BOL, LTI, Idorsia, and Pharma2B; receives payment for lectures at Abbvie, Sanofi‐Genzyme, Movement Disorder Society, Bial, and UCB; received research support from the Michael J. Fox Foundation, the National Parkinson Foundation, and the Israel Science Foundation as well as from Teva NNE program, Biogen; serves on the advisory board of LTI, NeuroDerm, Sionara, Sanofi‐Genzyme, Biogen, Denali, Intec Pharma, Idorsia; owns stocks in Lysosomal Therapeutic Ltd, Vibrant, BOL; and serves as a member of the Editorial Board for the Journal of Parkinson's Disease. A.O.U. has received research support from the Michael J. Fox Foundation and Chaya Charitable Fund and has received honoraria from Sanofi Genzyme., (© 2021 The Authors. Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring published by Wiley Periodicals, LLC on behalf of Alzheimer's Association.)