BACKGROUND Urban air pollution is a major threat to child and adolescent health. Children are more vulnerable to its effects, being associated with higher morbidity and mortality due to acute and chronic diseases, especially respiratory ones. A study is performed on the relationship between urban air pollution and the rate of hospital admissions due to acute respiratory diseases. METHODS An ecological study was conducted on young people under 17 years-old in the city of Murcia, who had visited hospital emergency departments due to respiratory diseases (ICD-9) during 2015. A logistic regression was performed on the risk of hospital admission that included consultations in relation to the average daily levels of environmental pollutants (NO2, O3, PM10, SO2) obtained from the Air Quality Surveillance and Control network of the Region of Murcia. Other control variables, such as gender, age, average daily ambient temperature, and season of the year. RESULTS A total of 12,354 (56% boys and 44% girls) children consulted in the emergency department for respiratory disease. Of those, 3.5% were admitted, with a mean age of 2.54 (95% CI; 2.16-2.91) years. The odds ratio (OR) of hospital admission for respiratory diseases: NO2 1.02 (95% CI; 1.01-1.04; P<.01), O3 1.01 (95% CI; 1.00-1.03; P<.01) male 1.4 (95% CI 1.11-1.79; P<.01) and winter 2.10 (95% CI 1.40-3.21; P<.01). Admissions for asthma: PM10 1.02 (95% CI; 1.01-1.04; P<.05), O3 1.04 (95% CI; 1.01-1.06; P<.01). Admissions for bronchiolitis: Age 0.69 (95% CI; 0.48-0.99; P<.05); NO2 1.03 (95% CI; 1.01-1.05; P<.01). CONCLUSIONS Urban air pollution increases hospital admissions in children due to acute respiratory diseases, especially asthma and bronchiolitis. Implementing preventive measures, expanding time series and collaborative studies with open data, would help improve public health and air quality in the cities.