Background: The mechanisms linking cerebral amyloid angiopathy (CAA) to enlarged perivascular spaces in centrum semiovale (CSO-EPVS) and whether other Alzheimer’s Disease (AD) pathologies might affect CSO-EPVS are unclear. We hypothesized that amyloid but not tau load would independently correlate with CSO-EPVS in CAA. Methods: Fifty prospectively enrolled nondemented probable CAA patients underwent high-resolution structural MRI, Pittsburgh compound B (PiB, for amyloid), and 18 F-flortaucipir (FTP, for tau) PET imaging. Microbleeds (all lobar, LMB) were counted and white matter hyperintensity volume (WMH) was quantified. CSO-EPVS were counted on T 2 -MRI sequence and graded using a previously validated scale (range 0-4). A multivariate ordinal regression model was used to assess the independent associations between CSO-EPVS and mean cortical amyloid as well as tau deposition, after adjusting for relevant covariates. Results: Patients had a mean age of 69.3±7.2. Age, sex, presence of hypertension, intracerebral hemorrhage (ICH), LMB counts, and WMH were not associated with CSO-EPVS grades (p>0.2 for all comparisons). Higher PiB uptake significantly correlated with increased CSO-EPVS (rho=0.45, p=0.001). Higher FTP showed a trend for correlation with CSO-EPVS (rho=0.26, p=0.069). In an ordinal regression model with CSO-EPVS grade as the dependent variable and both amyloid and tau levels included as predictors along with covariates presented above, the association of CSO-EPVS remained significant with higher PiB uptake (β=3.97, 95%CI 1.1-6.8, p=0.007) but not with FTP uptake (p=0.167). Conclusion: Results of this study suggest that CSO-EPVS is independently associated with amyloid but not with tau deposition in CAA. CSO-EPVS was not associated with age or classical vascular risk factors or presence of ICH. Our results support the view that vascular amyloid but not other AD pathologies such as tau might contribute to EPVS in patients with CAA.