<p>Considering that the aging of the world population is a relevant demographic phenomenon nowadays, the objective of this study was to compare the levels of well-being (emotional, psychological and social),&nbsp;the routes of access to well-being&nbsp;(pleasant life, engaged life and meaningful life) and the state of mental health (flourishing, moderate and languishing) between&nbsp;young-old people and old-old people&nbsp;in Buenos Aires. For this, a quantitative study of descriptive / comparative scope was carried out within a non-experimental design in a transverse time sequence and a sample of N = 634 subjects of both sexes between 65 and 100 years of age was formed, who completed an ad-hoc socio-demographic questionnaire; the Mental Health Continuum- Short Form and the Scale of three routes of access to well-being. The results showed that the young-old people obtained higher scores in all the study variables compared to the old-old ones. This was the first national and international study that used two contemporary models of well-being.</p>