Cross-cultural studies of neurodegenerative disorders are especially important when the disease in question is difficult to diagnose, particularly if symptoms of the illness include behavioral disturbances that may be interpreted differently in different cultures. One such disease is frontotemporal lobar degeneration (FTLD), an early-age-of-onset dementia that disproportionately affects social behavior. We report the demographic and neuropsychologic characteristics of more than 300 patients diagnosed with FTLD in the United States, Greece, and Turkey. We find that patients with the frontal variant of frontotemporal dementia (FTD) are diagnosed at an earlier age and report earlier symptom onset in the United States than in Greece or Turkey. Furthermore, neuropsychologic measures indicate that at diagnosis, FTD patients in the United States are less impaired than patients in Greece and Turkey. Patients with FTD in Greece and Turkey are diagnosed later in the disease, presumably because their behavioral symptoms are not easily detected by the medical system in these countries. Our study underscores the need to create culturally appropriate indices of the behavioral symptoms of FTLD, so that patients may be diagnosed and treated at an earlier stage.