Clinically, computerized tomography scanning and magnetic resonance imaging (MRI) are the neuroimaging techniques most frequently used in the work up of progressive cognitive impairment, in order to rule out tumors or other treatable etiologies. However, as we move closer to having more effective treatments for Alzheimer's disease (AD), we experience a greater need to use markers of early brain injury. Among them is neuroimaging. In this review we give some examples of the role of MRI and of functional MRI (fMRI) as markers of early brain changes. DEVELOPMENT: Regional metabolism, studied with positron emission tomography (PET) can also be used advantageously to depict early cortical changes in mild cognitive impairment (MCI) and even presymptomatic AD. SPECT, less expensive than PET, has a lower sensitivity, but has been extensively studied and using quantification methods can help even in MCI. Newer PET markers allow for the evaluation of activated microglia in vivo, as well as for the study of amyloid deposition in the brain and the activity of enzymes such as acetyl-cholinesterase. CONCLUSION: Future refinements in the neuroimaging techniques seem likely to help in the early diagnosis, evaluation of potential treatments and clarification of pathogenetic mechanisms in AD.