There is broad empirical evidence, but still a lack of theoretical explanations, for the phenomenon that most older people feel considerably younger than their real age. In this article, a measurement model of subjective age was assessed, and two independent theoretical approaches are proposed: (1) a motivational approach assuming that the age underestimation is a special form of self-enhancement; and (2) an information-processing approach assuming that elderly people look younger nowadays than formerly, which leads to an underestimation of their own age since people compare themselves to an age-prototype which is no longer accurate. Data from 792 adults aged 58-70 support the motivational approach, without ruling out the information processing approach. Data from a younger sample (42 students aged 20-35) provide evidence for the information processing approach additionally. Further, a path model suggests that bodily aspects are the strongest predictor of subjective age. (Contains 7 figures, 2 tables, and 3 footnotes.)