Background: The analysis of demographic tendencies indicates a continuing process of extending life expectancy in numerous societies. Alongside the decline in fertility, the continuing process of extending life expectancy is the primary cause for the aging of societies. An increasing percentage of the elderly require defining the welfare among older people and its factors. Aim: This article presents various views on successful aging and introduces the authorial Successful Aging Index model, which was the basis for a questionnaire diagnosing the quality of aging. The author’s intention was to create a diagnostic tool for said process. Conclusions: Presented tool according to the author can be very useful for diagnosing the course of successful aging. However, this requires additional empirical testing.