Objective. The purpose of this study is to assess the correlation between the FeNO (fractional exhaled nitric oxide) value and asthma severity. Material and method. A prospective study including 48 children aged 5 to 18 years, who have been diagnosed with asthma in „Victor Gomoiu” Children Clinical Hospital between May 2012 – November 2013, has been initiated. In the first stage of the study both the diagnosis and the degree of severity of asthma, using GINA 2008 guideline criteria, have been established, and the FeNO value has been measured before beginning any controller therapy. For the persistent asthma forms the controller therapy has been initiated, adapted to provide the controlled asthma status. In the next stage, after GINA 2014 guideline was published, a second classification of asthma, based on the degree of severity, has been performed, by taking into account the treatment step necessary to maintain the controlled asthma status, according to this new guide. Finally the correlation between FeNO value and the degree of asthma severity has been assessed, using first the asthma classification from GINA 2008 guideline and then the asthma classification from GINA 2014 guideline. Results. Among those 48 children included in the study 29 had normal FeNO value and 19 elevated FeNO value. According to GINA 2008 guideline criteria they have been included in the following severity asthma forms: 6 patients intermittent asthma, 27 patients mild persistent asthma, 14 patients moderate persistent asthma and 1 patient severe persistent asthma. According to GINA 2014 guideline criteria 25 patients have been labeled as mild asthma, 22 as moderate asthma and 1 as severe asthma. The statistic assessment of the correlation between asthma severity form according to GINA 2008 guideline and FeNO value provided a value of p = 0,278 and for the correlation between FeNO value and asthma severity form according to GINA 2014 guideline provided a value of p = 0,0468. Conclusion. FeNO value is not correlated with asthma severity as resulted from GINA 2008 guideline classification, but is correlated with asthma severity as resulted from GINA 2014 guideline classification.