An increasing number of studies suggest that executive functions are among the first cognitive functions to bear negative effects of normal aging. Executive functions also appear to be early affected in Alzheimer's disease and frontotemporal dementia. This article reviews studies in neuropsychology and experimental cognitive psychology with a focus on normal aging, Alzheimer's disease as well as frontotemporal dementia. Study results suggest that so called executive tasks are not equally impaired by normal ageing or dementia in agreement with the recent theoretical models, which state that a set of distinct elementary mechanisms subserve the executive control of cognitive behavior. These models are therefore particularly relevant to address issues stemming from aging.