<p>High concentrations of air pollutants have adverse effects on our health. They cause various diseases related to the respiratory and circulatory systems, leading to premature deaths. This paper aims to assess changes in PM_2.5 and NO₂ concentrations and to estimate how many premature deaths were caused by the pollutants analysed. The analysis was performed for the period from 2010 to 2019, for the major cities of Poland. For the analysis, annual average concentrations of PM_2.5 and NO₂ calculated on the basis of measurements available from the National Air Quality Monitoring (JPOAT) service were used. Health exposure assessment was performed in the AirQ + tool, and factors for estimating health effects were used in accordance with the recommendation of the AirQ + tool authors. From 2010 to 2019, the average annual concentration of PM_2.5 in most studied cities decreased. During this period, the highest reduction in concentration occurred in Wrocław, Warsaw, and Poznań. In contrast, the annual average NO₂ concentrations remained similar in most analysed cities. The exceptions are Wroclaw, where a significant decrease occurred, and Katowice, where concentrations significantly increased. The highest number of premature deaths due to high PM_2.5 and NO₂ concentrations occurred in Katowice and Cracow. High concentrations of PM_2.5 in the analysed cities caused approximately 7–10% of premature deaths, while high concentrations of NO₂ accounted for approximately 5–8% of premature deaths. PM_2.5 concentrations showed a steady decreasing trend, while NO₂ concentrations showed a decreasing or increasing trend, depending on the city. PM_2.5 concentrations showed a much higher reduction than NO₂. The percentage of premature deaths due to long-term exposure to PM_2.5 has reduced by about 5% between 2010 and 2019, and due to NO₂ by about 2%, and has increased in some cities.</p>