Objective: To assess the impact of new clinical diagnostic criteria for frontotemporal dementia (FTD) syndromes, including primary progressive aphasias (PPA), on prior clinical diagnosis and to explore clinicopathological correlations. Methods: 178 consecutive neuropathologically-ascertained cases initially diagnosed with a FTD syndrome were collected through specialist programs: the Cambridge Brain Bank, UK and Sydney Brain Bank, Australia. 135 cases were re-classified using the revised diagnostic criteria into behavioral variant (bvFTD), semantic variant PPA (sv-PPA), nonfluent/agrammatic variant PPA (nfv-PPA) and logopenic variant PPA (lv-PPA). Pathological diagnoses included FTLD-tau, FTLD-TDP, FTLD-FUS, FTLD-UPS, FLTD-ni and Alzheimer’s disease (AD). Statistical analyses included χ2 tests, analyses of variance and discriminant statistics. Results: Comparison of the original and revised diagnosis revealed no change in 90% of bvFTD and sv-PPA cases. By contrast 51% of nfv-PPA cases were reclassified as lv-PPA, with apraxia of speech and sentence repetition assisting in differentiation. Previous patterns of pathology were confirmed, although more AD cases occurred in FTD syndromes (10% bvFTD, ~15% sv-PPA and ~30% nfv-PPA) than expected. AD was the dominant pathology (77%) of lv-PPA. Discriminant analyses revealed that object agnosia, phonologic errors and neuropsychiatric features differentiated AD from FTLD. Conclusion: This study provides pathological validation that the new criteria assist with separating PPA cases with AD pathology into the new lv-PPA syndrome, and found that a number of diagnostic clinical features (disinhibition, food preferences and naming) did not assist in discriminating the different FTD syndromes.