Background: Childhood obesity is an important public health problem worldwide, while the effect of obesity on exhaled nitric oxide in children remains unclear. This study aimed to investigate the prevalence of obesity and overweight in Asian children in Taiwan, with emphasis on the influence of increasing weight status on fraction of exhaled nitric oxide (FeNO). Methods: Asian children aged 4 – 18 years (N = 5393) in the Prediction of Allergies in Taiwanese Children (PATCH) study were evaluated using questionnaires and anthropometric measurements. Single-breath online FeNO was measured in a sampling cohort of 1717 subjects that is representative of the source population. Results: With the use of the International Obesity Task Force (IOTF) criteria, the prevalence of obesity and overweight in children was 8.3% and 20.8%, respectively. The prevalence of obesity (11.5% of boys and 5.1% of girls) and overweight (23.0% of boys and 18.6% of girls) was significantly higher among boys than girls (both P