AbstractThe term Lewy body disease (LBD) encompasses a spectrum of neurodegenerative conditions, particularly Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB), associated with abnormal deposits of alpha‐synuclein in the brain and representing up to 20% of all neurocognitive disorders in memory clinics. Mild cognitive impairment or mild dementia precede or concur with Parkinsonism in the early stages of DLB and in a third of patients with PD at diagnosis. However, when Parkinsonism is slightly detectable, the differential diagnosis from other dementing conditions, such as Alzheimer’s disease (AD), may be challenging. For this reason, neuroimaging and electrophysiological biomarkers, divided into indicative or supportive based on their diagnostic performance over or below 80%, assist the clinical reasoning to increase the likelihood that MCI/early dementia is associated with LB. The European Intersociety Consensus Diagnostic Task Force recommends prioritizing the Dopamine transporter (DaT)‐SPECT imaging to investigate nigro‐striatal degeneration as the first biomarker (sensitivity 76%, specificity 88%), and suggests subsequently [123I]‐MIBG cardiac scintigraphy to evaluate the postganglionic sympathetic denervation in those cases (about a quarter) where DaT‐SPECT is negative but DLB is still clinically possible (AD pathology is estimated to be underlying in about 86% of these cases). In the absence of well‐validated techniques to establish the presence of brain alpha‐synuclein aggregates in vivo, the proposed sequence of biomarkers will provide the most accurate and cost‐effective biomarker‐based diagnosis of LBD.