One of the aims of research on well-being is to discover the factors that either increase or decrease well-being, in both young and old people. Many factors have been studied in relation to well-being, but only some have been found to be associated with it. These factors are demographic (age, sex, culture, marital status), social (socioeconomic status, having children, religion, social contacts) or are related to personality, life events, health, and activities. However, some of these factors have a stronger association than others. This article gives a brief review of this research with special focus on the elderly.