Diagnosing dementia with Lewy bodies (DLB) is challenging as symptoms are heterogenous and not specific to the disease. Here we present a clinicopathologic series of false-positive DLB cases. Patients were enrolled retrospectively from the Netherlands Brain Bank when they met the clinical criteria of probable DLB, but with a pathologic diagnosis other than DLB or Parkinson’s disease dementia. Twenty-two false-positive cases were selected. Alzheimer disease with or without copathology was the most common (64%) pathologic diagnosis. Other pathologic diagnoses, such as frontotemporal dementia, multiple-system atrophy, Creutzfeldt-Jakob disease, and autoimmune encephalitis, were also encountered. Atypical clinical signs for DLB were present in almost half of the cases and could be a trigger to consider other diagnoses than DLB. Additional diagnostic examinations, feedback of pathologic diagnosis, and the creation of a set of clinical features that are indicative of other conditions, could reduce the amount of false-positive DLB cases.