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Introduction Apraxia is common in neurodegenerative dementias but underrepresented in clinical workup for differential diagnoses. Methods Praxis-profiles were assessed with the Dementia Apraxia Test in 93 patients with early stages of biologically supported Alzheimer's disease or frontotemporal lobar degeneration: semantic primary-progressive aphasia, nonfluent primary-progressive aphasia, and behavioral variant frontotemporal dementia. Associations with core cognitive deficits of the dementia subtypes (i.e., visuospatial, sociocognitive, and semantic-linguistic) were explored. Results Patients showed significant apraxia compared with healthy controls but also disease-specific praxis-profiles. Using only the Dementia Apraxia Test, all four dementia subtypes could be correctly discriminated in 64.4% of cases, and in 78.2% when only distinguishing Alzheimer's disease versus frontotemporal lobar degeneration. Praxis-profiles showed consistent associations with core cognitive impairments of the different dementia subtypes. Discussion The Dementia Apraxia Test is a valid, time-efficient and versatile cognitive marker to delineate variants of frontotemporal lobar degeneration and Alzheimer's disease in clinical routine, facilitating differential diagnoses of dementia subtypes in early disease stages., Highlights • AD and FTLD variants share common deficits in standard cognitive domains. • Apraxia is common in these diseases but rarely used as a clinical marker. • Praxis was assessed in 93 patients with AD and clinical FTLD variants. • Specific praxis-profiles emerged for AD, bvFTD, svPPA and nfPPA. • AD and FTLD variants may be clinically differentiated by praxis-profiles.