Healthy mental ageing may be defined as the absence of the common disabling mental health problems of older people, especially cognitive decline and depression, accompanied by the perception of a positive quality of life. Older people are particularly prone to negative effects on mental health due to poor physical health. Modifiable aspects of lifestyle have been shown to be associated with healthy mental ageing. These include increased physical activity, intellectual stimulation (including education), avoidance of smoking and various aspects of diet. There is reasonably strong evidence that the treatment of hypertension will decrease the risk of cognitive impairment, and moderate alcohol intake may also have some benefits on cognition. These modifiable lifestyle factors may benefit from deliberate individual and population health promotion strategies to maximize mental health in old age, although to date intervention trials have not been performed to support the evidence obtained from observational studies.