OBJECTIVES: To investigate the use of asthma medication and occurrence of asthma exacerbations up to 5 years before and after the onset of type 1 diabetes mellitus (T1DM) in children and adolescents. METHODS: Children and adolescents younger than 1years with at least 2 insulin prescriptions between 1999 and 2009 classified as T1DM cohort (n = 915) and a 4 times larger reference cohort (n = 3,590) with the same age and gender were identified from the Dutch PHARMO Record Linkage System. The date offirst insulin dispensing was selected as the index date. RESULTS: The 5-year prevalence rate of asthma medication use in the T1DM cohort (23.2%) was significantly higher than the reference cohort (18.3%) after the onset of diabetes. No statistically significant difference between the two cohorts was observed in the use of specific types of asthma medication except for short acting muscarinic antagonists that were significantly more used in the T1DM cohort (5.5%) compared with the reference cohort (0.62%) after the onset of diabetes. The incidence rate of asthma medication use declined over time with a peak in the T1DM cohort the 1st year after the onset of diabetes. Furthermore, 1 year after the index date there was a peak in incidence rate of asthmaexacerbations in both T1DM (7.8 per 1,000 person year) and reference (6.8 per 1,000 person year) cohorts. CONCLUSIONS: T1DM is associated with statistically significantly higher asthma medication use after the onset of T1DM, especially in the 1st year after the onset of diabetes. Pediatr Pulmonol. 2016;51:1113-1121. (c) 2016 Wiley Periodicals, Inc.