Cognitive deficits beyond memory impairment, such as those affecting language production or executive functioning, can be useful in clinically distinguishing between dementia syndromes. We tested the hypothesis that Ashkenazi Jewish (AJ) patients who have dementia with Lewy bodies (DLB) and carry glucocerebrosidase (GBA) mutations will have verbal fluency deficits different from those found in Alzheimer disease (AD), whereas AJ patients with DLB who have no GBA mutations will have similar deficits in verbal fluency to those found in AD. We compared performance in phonemic and semantic verbal fluency tasks in 44 AJ patients with DLB and 20 patients with AD, matched for age, education, and age of immigration. All groups were found to have a deficit in semantic verbal fluency. On conducting the phonemic task, patients with DLB who carried GBA mutations scored more poorly than patients with AD, whereas DLB-noncarriers performed similarly to patients with AD. We suggest that verbal fluency tasks could serve as a possible clinical marker to subtype patients with DLB, with phonemic fluency being a marker for GBA-associated DLB.