Behaviour change is increasingly recognised as a common feature of amyotrophic lateral sclerosis (ALS), and may be similar to that seen in frontotemporal dementia (FTD). The behaviours most disturbed in ALS, and those that relate most significantly to caregiver burden, however, have not been well established. Forty ALS participants and their caregivers, and 27 age- and gender-matched healthy controls and their relatives, participated in this study. ALS participants were assessed on a disease rating scale, and caregivers and control informants completed the revised version of the Cambridge Behaviour Inventory and a measure of burden. ALS caregivers reported significantly more disturbance than healthy control informants on the functional domains of everyday skills, self-care, and sleep, and in the behavioural domains of mood and motivation. There were no differences between groups in frequency of memory and orientation difficulties, or behaviours characteristic of FTD, such as changes to eating habits or stereotypic and motor behaviour, indicating that the behavioural profile in ALS may differ from FTD. In the ALS group, the domains with the strongest relationship to caregiver burden were everyday skills, motivation and memory, likely because poor motivation, memory dysfunction and difficulties completing activities of daily living require more carer support via direct supervision, prompting or hands on care. Services to support ALS patients and caregivers need to provide targeted interventions for those functional and behavioural changes which are most burdensome in the disease.