The study was aimed to investigate the effects of air pollutants particulate matter (PM_2.5, PM₁₀), sulfur dioxide (SO₂) and NO₂ on hospital admissions for respiratory diseases in the residents of Nis, Serbia, during the period 2012-2014. The findings of average daily concentrations of air pollutants were obtained both by the measurements made by the Public Health Institute Nis and by the state ambient air quality monitoring network of the Agency for Environmental Protection of the Republic of Serbia. The respiratory diseases analyzed in the study are pneumonia, asthma, and chronic obstructive pulmonary disease (COPD). Patients were categorized into three age groups (0-17.9, 18-64.9 and >65). Poisson regression was used to examine the link between air pollutants and respiratory health outcome at lag 0. Results was expressed as the increase in Relative Risk (RR) for hospital admissions for each daily increase in air pollutants for 10 μg/m³. NO₂ had the most significant effect on hospital admission, although its concentrations did not exceed the prescribed values. With an increase in the daily NO₂ concentrations of 10 μg/m³, the RR of daily asthma and COPD hospital admissions in Nis older than 65 years increased by 1.2% and 0.7%, respectively. In women older than 65 years, with an increase in daily concentrations of NO₂ of 10 μg/m³, the risk of daily hospital admissions for asthma increased by 1.5%. In multi-polluted statistical analysis (adjusted with PM_2.5 and SO₂) each daily increase in NO₂ for 10 μg/m³ was statistically significant associated with the increased RR by 1.3%. In men 18 to 64 years of age, with an increase in daily NO₂ concentrations of 10 μg/m³, the RR of hospital admissions for asthma increased by 2.0%, and in the PM_2.5-adjusted model, increased by 1.8%. The suspended particles had an effect on hospital admission for pneumonia in men up to 17.9 years of age. With an increase in daily concentrations of suspended PM_2,5 particles of 10 μg/m³, the risk of hospital admissions for pneumonia in them increases by 0.6% and 0.4%, respectively. We found that the concentration of NO₂ even lower of national limit value had the greatest impact on hospital admission due to COPD in elderly men and asthma in elderly women. Suspended particles had a significant effect on hospital admission for pneumonia in younger men.