Introduction: Cough exceeding 3-8 weeks was defined as chronic cough in various guides. Asthma is the most common cause of chronic-specific cough. Causes other than asthma include prolonged bacterial bronchitis and upper airway cough syndrome (UACS). Nitric oxide (NO) causes vascular smooth muscle relaxation, bronchodilation, and oxidant effects via its metabolite, peroxynitrite. An increase in NO results in inflammation, vasodilatation, and bronchial edema. Materials and Methods: The study group included 90 patients aged 6-17 years selected from individuals presenting to the Pediatric Immunology and Allergic Diseases Clinic with cough persisting for 4 weeks and 30 other patients representing to the control group. Patients with a history of premature birth and long-term ventilatory support, neuromotor retardation, or chronic lung and heart disease received systemic corticosteroid therapy in the previous 4 weeks, a chest deformity, with any chronic disease or received immunotherapy were excluded from the study. Results: The most common diagnosis among the 90 patients in this study was asthma, observed in 27 (30%). Fractional exhaled NO values were highest in the asthma group at 39.5 +/- 26.6 parts per billion (ppb) and lowest in the UACS group at 11.6 +/- 4.0 ppb. Values in the control group were 17.8 +/- 11.1 ppb. The differences between the groups were statistically significant (P < 0.001). Conclusion: Fractional exhaled NO measurement can be used as a quick and reliable diagnostic method in patients presenting with chronic cough due to its high positive predictive value, its practical nature, the fact that it is a noninvasive method and that it does not require the use of medication.