Objectives: The objective of the present modeling was to assess the population health impact of introducing Reduced-Risk Products (RRP) in countries where such products are already, or may be, marketed. The modeling reported here addresses the IQOS® heat-not-burn tobacco product in four countries: Japan, Italy, Singapore, and the U.S. Methods: The Population Health Impact Model was used to estimate the reduction of smoking attributable deaths and years of life saved (YLS) following the introduction of IQOS. The model predicts YLS due to lung cancer, ischemic heart disease, stroke, and chronic obstructive pulmonary disease by considering two scenarios: a null scenario without IQOS and an RRP scenario with IQOS. Modeling predictions are based on hypothetical Japanese, Italian, Singaporean, and American populations for the period of 1990–2010. Simulations were run to predict YLS by introducing IQOS in those countries, from data available in markets where IQOS is present. Results: The predicted YLS over the 20-year simulation period are presented following the introduction of IQOS in the U.S. and Italy at 17% uptake after 10 years (15% exclusive IQOS use and 2% dual use) and Japan and Singapore at 55% uptake (48% exclusive IQOS and other RRP use and 7% dual use). The modeling assumes that a majority of RRP uptake comes from current adult smokers switching to IQOS and that the effective dose of IQOS is 20% of that of cigarette smoking. The results demonstrate 0.96 million YLS for Japan, 0.11 million for Italy, 0.03 million for Singapore, and 1 million for the U.S. over the 20-year period. Conclusions: Modeling the population YLS upon introducing IQOS allows for a comprehensive assessment of the population health impact. The results demonstrate that an RRP can further reduce the overall population health impact in four countries with different smoking habits and RRP uptake, in addition to existing tobacco control efforts.