Background: Dupilumab, an anti-IL-4 receptor alpha monoclonal antibody, has been recently approved for the treatment of chronic rhinosinusitis with nasal polyps (CRSwNP) and moderate to severe asthma, demonstrating a rapid onset of clinical effects. CRSwNP is characterized by an extended type-2 inflammatory involvement that can be assessed by extended nitric oxide analysis. Objective: In this study we investigated whether Dupilumab is associated with a rapid improvement in extended nitric oxide parameters, lung function and clinical outcomes in patients with CRSwNP. Methods: Consecutive patients with CRSwNP and indication to be treated with Dupilumab were evaluated for extended nitric oxide analysis (exhaled, FENO; bronchial, JawNO and alveolar, CalvNO components; nasal, nNO) and lung function 15 and 30 days after treatment initiation, and for clinical outcomes (nasal polyps score, NPS; quality of life questionnaires; visual analogue scales, VAS, for main symptoms, asthma control test, ACT) after 30 days of treatment initiation. Results: 33 patients were enrolled. All extended nitric oxide and lung function parameters significantly improved after 15 days of treatment remaining stable at 30 days. NPS, VAS for main CRSwNP symptoms, quality of life questionnaires and ACT significantly improved after 30 days of treatment initiation. Conclusions: Dupilumab is associated with very rapid improvement in type 2 inflammation in all airway districts and this is associated with improved lung function and clinical parameters in patients with CRSwNP.