Despite its large use, recommendations for the use of brain F-18 FDG-PET in clinical practice were still lacking. The European Academy of Neurology (EAN) and the European Association of Nuclear Medicine (EANM) promoted a concerted action with 7 specialists from the two Societies and a group of facilitators in order to make the point on this issue. Extensive literature review and analysis of available data led, together with expert opinion (Delphi consensus), to deliver these recommendations that cover practically all the main brain neurodegenerative conditions causing cognitive impairment. Although the formal evidence in available literature is still limited, at the end of the process FDG-PET has been recommended to support clinical diagnosis in patients with Mild Cognitive Impairment (and thus possibly in the prodromal stage of a neurodegenerative disease), in patients with dementia of uncertain origin, to differentiate dementia from cognitive impairment of depression, and to help physicians in diagnosis atypical parkinsonisms as well as to pick up the neural basis of cognitive impairment in Parkinson’s disease patients. Also, the panelists recommended the use of sound semi-quantitative tools to assist the reporting. On the other hand, the panel did not recommend, at the present state of knowledge and therapeutic options, the use of brain FDG-PET in asymptomatic subjects at risk of developing a neurodegenerative disease, in patients with only subjective cognitive complaints, and in some less frequent conditions in which other diagnostic tools are judged to be more validated, such as amyotrophic lateral sclerosis and Huntington’s chorea. These recommendations have been reviewed by both the EAN and EANM boards, and are to be meant as ‘interim’ ones, ready to be updated once new evidence will accumulate. Physicians dealing with neurodegenerative conditions can now find an updated and easy-to-use guidance on when and why to use brain FDG-PET to be assisted in their diagnostic process. Also, patients and caregivers can now have a clear comprehension of the utility and limitations of this precious, non-invasive molecular imaging tool that is nowaday largely available in Europe with a reasonable cost and limited radiation exposure.