BACKGROUND: The in vivo diagnosis of cerebral amyloid angiopathy (CAA) is inferred from clinical and structural imaging features. (11)C-Pittsburgh compound B (PIB) is a PET ligand that binds to beta-amyloid in extracellular plaques and vessel walls. We hypothesized that patients with a clinical diagnosis of CAA-related hemorrhage (CAAH) have increased (11)C-PIB uptake and that the pattern differs from Alzheimer disease (AD). METHODOLOGY: Patients with CAAH based on established clinical criteria were studied using (11)C-PIB PET and were compared with age-matched controls and patients with AD. Distribution volume ratio (DVR) parametric maps were created using the cerebellar cortex as a reference region. RESULTS: Twelve patients with CAAH of mean age 73.9 (range 58-93) years were compared with 22 normal controls and 13 patients with AD of mean age 71.8 (59-83) and 73.8 (56-90) years, respectively. CAAH PIB median DVR binding was higher in cortical regions (1.69, interquartile range 1.44-1.97) compared with controls (1.32, 1.21-1.44, p = 0.002) but lower than AD (2.04, 1.93-2.26, p = 0.004). The occipital-global uptake ratio was lower among patients with AD than among patients with CAAH (p = 0.008), and the frontal-global uptake ratio was higher (p = 0.012). CONCLUSION: (11)C-Pittsburgh compound B (PIB) binding is moderately increased in most patients with probable cerebral amyloid angiopathy (CAA)-related intracerebral hemorrhage. The distribution may differ from that seen in Alzheimer disease. (11)C-PIB PET may assist in the in vivo diagnosis of CAA and serve as a surrogate marker for future therapeutic studies.