Cognitive impairment in nondemented ALS patients has been demonstrated, although its incidence remains to be determined. FTD is the most frequently form of dementia in ALS. The clinical profile of patients with dementia or mild cognitive deficit evokes neuropsychological deficits and behavioural changes resulting from executive dysfunction. The psychometric evaluation, centred on executive disturbances, goes with behavioural scales in order to accurately appreciate the repercussion of cognitive and behavioural changes on daily life.