There is increasing concern about the air quality of Istanbul because of increasing emission sources and their possible health effects. This study aims to assess the effects of air pollutants (PM10, PM2.5, and NO2) on hospital admissions for asthma, chronic obstructive pulmonary disease (COPD), and acute bronchitis to better understand the association between air pollution and respiratory diseases in the city. In order to investigate the health effects of air pollutants (Excess Relative Risk, ERR), a time-series analysis of daily respiratory hospital admissions and outdoor air pollutants was performed using single-pollutant Poisson generalized linear model (GLM) over a 5year period (2013-2017) at different time lags (0-9). Our results show that air pollutants have significant immediate and delayed effects on hospital admissions depending on different diseases. NO2 and PM2.5 have the highest risk effects on the hospital admissions. An increase in the PM2.5 level by 10 mu g/m3 increased admission rates for acute bronchitis by 8.06 % (95 % CI: 3.36-19.4 %) at lag 9 according to our results. This study showed that air pollution is associated with increased hospital admissions for some of the most common and serious respiratory diseases in Turkey.