ALS and frontotemporal dementia (FTD) utilize different functional rating scales: the ALSFRS-R assesses physical disability whereas the Frontotemporal Dementia Rating Scale assesses behavioural and functional impairment to produce an index of dementia staging. To better consider the applicability of the FRS in an ALS population, 130 patient-carer dyads were investigated. Scores on the ALSFRS-R and FRS were not significantly correlated (r(s) = 0.12, p > 0.10). Furthermore, patients with mild physical disability may rate as severe on the FRS; conversely, individuals who are severely physically disabled may exhibit very few behavioural symptoms. Measures typically used in ALS studies do not fully encapsulate the range of clinical symptoms, particularly from a behavioural perspective.