Introduction. The fraction of exhaled nitric oxide (FeNO) is used as a non-invasive biomarker that reflects inflammation in the airways. It is so versatile that it used to control asthma severity as well as to monitor response to treatment. However, the exact cut-off point of the nitric oxide level which allows one to make a precise diagnosis of asthma is unclear. Aim. To examine the possibility of using advanced statistical methods such as receiver operating characteristic for the analysis of FeNO concentrations for improving the diagnosis of asthma. Materials and methods. Receiver operating characteristic (ROC) was used for analyzing results to determine levels of nitric oxide which may be a prognostic indicator of asthma. The studied group consisted of 111 children including 69 asthmatic patients, and 42 age- and sex-matched healthy subjects. Measurement of exhaled nitric oxide was conducted in all subjects included in this study. Results. FeNO level was higher in asthmatic patients. The analysis of results showed that the cut-off point for the FeNO concentration is 11.5 ppb. Sensitivity and specificity with the FeNO level allowed us to determine a value of the diagnostic variable of FeNO concentration of 14.0 ppb. A comparison of FeNO level and sex of the subjects showed there is no correlation between these parameters of patients. Conclusions. Currently, the FeNO measurement provides complementary data in the care of a patient suffering from asthma, however analysis of more studies on a larger group of patients is needed.