Background The analysis of exhaled breath condensate may provide valuable insights into inflammatory and other metabolic processes of the lungs. However, its collection by active exhalation with conventional methods is cumbersome, demands a substantial level of co-operation with high motivation and is very difficult or impossible in children younger than about 4–6 years or in the elderly. A comfortable, noninvasive and efficient method is desirable. Design and patients For collection a high-performance pump connected to a cold trap and nasal prongs were used. The volume of the condensate collected was assessed in 141 children of all ages and five adults. As an example for a low molecular component, H2O2 a marker of oxidative stress, was determined fluorometrically. Results On average, in healthy children from 4 weeks to 18 years of age, 84·0 (79·4, 87·3) µL min−1 of nasally exhaled air condensate were collected. The volume obtained was about 45% less in 1–6-year-old children, increased linearly with collection time, and averaged about 20–30% of the exhaled water vapour. The concentration of H2O2 in the healthy children was 0·49 (0·48, 0·61) μM and did not depend on age, the time of the day, family, or personal history of atopy and sex. Conclusions The method described is generally applicable, comfortable, noninvasive, safe and efficient and allows the collection of nasally exhaled air condensate for the evaluation of metabolic processes of the lungs.