The use of objective outcome measures that assess airway inflammation in pediatric asthma can provide a good evaluation of asthma severity and treatment response. In this double-blind and randomized study the effects of 200 micro g of budesonide and 800 micro g of budesonide on markers of inflammation (exhaled nitric oxide (eNO), eosinophil protein X (EPX) excretion in urine) and on lung function (FEV (1)) were prospectively investigated in 24 ICS-naive children with mild persistent to moderate persistent asthma over a period of eight weeks. After eight weeks of treatment 200 micro g and 800 micro g of budesonide led to a significant decrease (p < 0.025) in eNO [median (90 % interval): 200 micro g: - 17.2 ppb (- 54.6 to 0.9); 800 micro g: - 13.2 ppb (- 44.6 to - 1.7)]. A significant change in urinary EPX excretion was only observed in the high dose group [200 micro g: - 10.3 micro g/mmol creatinine (- 116.2 to 50.5), p = 0.9; 800 micro g: - 49.2 micro g/mmol creatinine (- 231.0 to 48.7), p = 0.02]. However, a significant difference between the change from baseline after 8 weeks of either group was found neither for eNO (p = 0.66) nor for EPX excretion (p = 0.04). In conclusion, our data demonstrate that 800 micro g budesonide per day did not show any advantage in reduction of airway inflammation, measured by eNO and urinary EPX excretion, in children with mild persistent to moderate persistent asthma.