The study should create data for the selection of a clinically relevant primary endpoint to assess the efficacy and safety of Buparid/PARI SINUS as compared to Budes Nasal Spray in the therapy of chronic rhinosinusitis (CRS) with polyposis nasi in adult patients. Ideally, the selected parameter should allow a correlation between an objective methodology and the clinical outcome of the study patients.

Inclusion Criteria:

• Patient with confirmed diagnosis of chronic rhinosinusitis (CRS) with polyposis nasi grade I-III
• Patient with a PNIF of > 7 l/min separated for left and right side of the nose
• Patient's written informed consent
• Male or female,>= 18 years of age
• Patient is able to undergo nasal therapy without restrictions
• Capable of understanding the purpose and risk of the clinical trial
• Female patients with childbearing potential must have a negative urine pregnancy test prior to first IMP administration
• Patient has completed correctly the diary during the Wash-in Phase

Exclusion Criteria:

• Patients with cystic fibrosis
• Patients with polyposis nasi grade IV
• Patients with prior sinonasal surgery (exemption: polypectomy)
• Patients with primary ciliaritis
• Pregnant or breastfeeding women
• Patients with suspected active upper airway infection
• Receipt of an investigational drug as part of a clinical trial within 4 weeks prior to first administration of IMP
• Drug or alcohol abuse
• End-stage malignancies
• Known hypersensitivity to Budesonide
• Patients with oral steroid therapy within the last 4 weeks
• Patients with frequent epistaxis (> 2 per month)

Each participant has been monitored for adverse events up to 48 weeks. All patients withdrawn from the study will be followed-up for AEs or SAEs for further 2 weeks or 4 weeks, respectively.