Objective: To determine whether amyloid imaging with the positron emission tomography (PET) agent Pittsburgh compound B (PiB) can detect vascular β-amyloid (Aβ) in the essentially pure form of cerebral amyloid angiopathy associated with the Dutch-type hereditary cerebral amyloid angiopathy (D-CAA) mutation. Methods: PiB retention in a cortical composite of frontal, lateral, and retrosplenial regions (FLR) was measured by PiB-PET in 19 D-CAA mutation carriers (M +; 13 without neurologic symptoms, 6 with prior lobar intracerebral hemorrhage) and 17 mutation noncarriers (M −). Progression of PiB retention was analyzed in a subset of 18 serially imaged individuals (10 asymptomatic M +, 8 M −). We also analyzed associations between PiB retention and cerebrospinal fluid (CSF) Aβ concentrations in 17 M + and 11 M − participants who underwent lumbar puncture and compared the findings to PiB-PET and CSF Aβ in 37 autosomal dominant Alzheimer disease (ADAD) mutation carriers. Results: D-CAA M + showed greater age-dependent FLR PiB retention (p < 0.001) than M −, and serially imaged asymptomatic M + demonstrated greater longitudinal increases (p = 0.004). Among M +, greater FLR PiB retention associated with reduced CSF concentrations of Aβ40 (r = −0.55, p = 0.021) but not Aβ42 (r = 0.01, p = 0.991). Despite comparably low CSF Aβ40 and Aβ42, PiB retention was substantially less in D-CAA than ADAD (p < 0.001). Interpretation: Increased PiB retention in D-CAA and correlation with reduced CSF Aβ40 suggest this compound labels vascular amyloid, although to a lesser degree than amyloid deposits in ADAD. Progression in PiB signal over time suggests amyloid PET as a potential biomarker in trials of candidate agents for this untreatable cause of hemorrhagic stroke. ANN NEUROL 2019;86:616–625.