There are two theories regarding post-retirement consumption: Many researchers believe that consumption increases with age. While some argue that an increase in ag (post-retirement) leads to a sharp and sudden decrease in consumption. Therefore, this study examines the effect of population structure on life- cycle consumption for two different time.  For the country of Iran, the ARDL model was used in 1960 to 2021, and for a group of selected countries (158 countries), the GMM model was employed in 2001 to 2021. The results of both models have indicated a negative effect of Real GDP per capita, and positive impacts of population growth, youth dependency ratio and the elderly dependency ratio variables on the consumption, share in GDP. Also, the results of the error correction model for Iran showed that the consumption, share in GDP returns to its long-term balance approximately after 1.5 periods following any short-term imbalance., The life- cycle hypothesis has also been confirmed for Iran and the group of selected countries. Regarding the retirement consumption puzzle, it can be stated that consumption increases with age in Iran and the group of selected countries.