The increase in butyrylcholinesterase (BChE) activity in the brain of Alzheimer disease (AD) patients and animal models of AD position. This enzyme as a potential biomarker of the disease. However, the information on the ability of BChE to serve as AD biomarker is contradicting, also due to scarce longitudinal studies of BChE activity abundance. Here, we report 11C-labeling, in vivo stability, biodistribution, and longitudinal study on BChE abundance in the brains of control and 5xFAD (AD model) animals, using a potent BChE selective inhibitor, and positron emission tomography (PET) in combination with computerised tomography (CT). We correlate the results with in vivo amyloid beta (Aβ) deposition, longitudinally assessed by florbetaben-PET imaging.