© 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd. This is the protocol for a review and there is no abstract. The objectives are as follows: To determine the diagnostic test accuracy (DTA) of the 18F PET ligands for Aβ (18F-Florbetapir, 18F-Florbetaben, and 18F-Flutemetamol) as the index tests for detecting participants with mild cognitive impairment (MCI) at baseline who would clinically progress to Alzheimer's disease dementia (ADD), or other forms of non-ADD, or any form of dementia at follow-up. To investigate the heterogeneity of the DTA in the included studies, we will evaluate the spectrum of people, referral centres, clinical criteria of MCI, 18F PET ligands for Aβ (18F-Florbetapir, 18F-Florbetaben, and 18F-Flutemetamol) techniques, reference standards used, duration of follow-up, aspects of study quality, and conflicts of interest.