Epidemiologic studies suggest increased asthma prevalence in obese subjects. However, the relation between obesity and airway inflammation remains unclear. This cross-sectional study aims to investigate the relation between obesity indices and exhaled nitric oxide (ENO) and leukotriene B(4) (LTB(4)) in children with asthma. Asthmatic patients aged 7-18 yr old were recruited. Weight-for-height Z score was calculated from anthropometry. ENO was measured by online single-breath method using a chemiluminescence analyzer, whereas LTB(4) concentrations in exhaled breath condensate (EBC) were quantified using competitive enzyme immunoassay. Ninety-two asthmatics and 23 controls were recruited. The mean ENO and LTB(4) concentrations in EBC were higher in asthmatic patients (87 p.p.b. and 40.5 pg/ml) than controls (25 p.p.b. and 18.7 pg/ml) (p < 0.0001 for both). Obesity, as defined by weight >120% median weight-for-height, was not associated with any alteration in ENO or LTB(4) concentrations in patients with asthma. Besides, these inflammatory markers did not differ between asthmatics in the highest and lowest quartiles of weight-for-height Z score. On multivariate analysis, ENO showed significant correlation with age (beta = 0.511, p < 0.0001), peripheral blood eosinophil count (beta = 0.222, p = 0.019), plasma total IgE concentration (beta = 0.187, p = 0.050) and forced expiratory volume in 1-s (FEV(1); beta = -0.221, p = 0.014). None of the factors was associated with LTB(4) concentration in EBC. In conclusion, ENO and LTB(4) concentration in EBC are increased in childhood asthma. However, these inflammatory markers did not differ between obese and non-obese children with asthma.