The presence of sinusitis, as well as rhinitis, in adult asthmatic patients is a very serious problem, because rhinosinusitis, in many cases of adult asthma, is expected to be eosinophilic chronic rhinosinusitis, which is characterized by bilateral nasal polyps, ethmoidal antrum-dominant lesions, and losing the sense of smell.12 This type of rhinosinusitis, which occurs mainly in adults, is resistant to macrolide therapy, and is sometimes accompanied by sinus and peripheral blood eosinophilia.13,14 According to the retrospective data on FeNO measured in Gunma University Hospital, by the American Thoracic Society/European Respiratory Society-recommended online method, FeNO levels in 12 patients, who complained of olfactory dysfunction and who showed abnormal shadows in bilateral ethmoid sinuses on CT or MRI, were higher than those of asthmatic patients who had not complained of olfactory dysfunction, although both groups had been treated by controller medications for asthma (74.5±35.4 ppb versus 37.3±24.9 ppb; n=12 versus n=58). This observation motivated us to develop the G scale containing the question on olfactory dysfunction. As expected, FeNO was significantly more elevated in asthmatic patients with olfactory dysfunction than in other asthmatic patients, even if their asthma had been treated adequately by standard therapy. Because the diagnosis of rhinosinusitis was not made by CT, MRI imaging, or rhinoscopy in the present study, one can only conclude that olfactory dysfunction, as one of the subjective symptoms, was related to FeNO levels. Although olfactory dysfunction is a representative symptom of eosinophilic sinusitis or nasal polyps, this symptom is not specific for eosinophilic sinusitis or nasal polyps.