Climate change is expected to increase heat-related mortality across the world. Health Impact Assessment (HIA) studies are used to quantify the impact of higher temperatures, taking into account the effect of population adaptation. Although air-conditioning (AC) is one of the main drivers of technological adaptation to heat, the health impacts associated with AC-induced air pollution have not been examined in detail. This study uses the city of Thessaloniki, Greece as a case study and aims to estimate the future heat-related mortality, the residential cooling demand, and the adaptation trade-off between averted heat-related and increased air pollution cardiorespiratory mortality. Using temperature and population projections under different Coupled Model Intercomparison Project Phase 6 (CIMP6) Shared Socioeconomic Pathways scenarios (SSPs), a HIA model was developed for the future heat and air pollution cardiorespiratory mortality. Counterfactual scenarios of either black carbon (BC) or natural gas (NG) being the fuel source for electricity generation were included in the HIA. The results indicate that the heat-related cardiorespiratory mortality in Thessaloniki will increase and the excess of annual heat-related deaths in 2080-2099 will range from 2.4 (95% CI: 0.0-20.9) under SSP1-2.6 to 433.7 (95% CI: 66.9-1070) under SSP5-8.5. Population adaptation will attenuate the heat-related mortality, although the latter may be counterbalanced by the higher air pollution-related mortality due to increased AC, especially under moderate SSP scenarios and coal-fired power plants. Future studies examining the health effects of warmer temperatures need to account for the impact of both adaptation and increased penetration and use of AC.