Buparid/PARI SINUS Versus Budes® Nasal Spray in the Therapy of Chronic Rhinosinusitis

Inclusion Criteria: * Patient with confirmed diagnosis of chronic rhinosinusitis * Patient without alternative other than sinus surgery * Patient's written informed consent obtained prior to any screening or study-specific procedure * Male or female, ≥ 18 years of age * Patient is able to undergo nasal therapy without restrictions * Capable to correctly use the PARI SINUS device * 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 is able to participate in the study according to Investigator's opinion Exclusion Criteria: * Patients with cystic fibrosis * Patients with polyposis nasi grade I-IV * Patients with prior FESS (Functional Endoscopic Sinus Surgery) * Pregnant or breastfeeding women * Any active invasive bacterial, viral or fungal infection within one week prior to first investigational medicinal product (IMP) administration * No clinically relevant abnormal parameters of vital signs, blood biochemistry or renal/hepatic function * Unlikely to comply with visits, inhalation procedures or other measurements scheduled in the protocol * Receipt of an investigational drug as part of a clinical trial within 4 weeks prior to first administration of IMP * Any co-existing medical condition that in the Investigator's judgement will substantially increase the risk associated with the patient's participation in the clinical trial * Psychiatric disorders or altered mental status precluding understanding of the informed consent process and/or completion of the necessary procedures * Drug or alcohol abuse * End-stage malignancies * Known hypersensitivity to Budesonide * Patients with oral steroid therapy within the last 3 months * Patients needing \> 1 mg/day Budesonide (or steroidal equivalent) for therapy of asthma * Patients on therapy with leukotriene-receptor antagonists, decongestants, antihistamines or antibiotics * Patients with frequent epistaxis (\> 1 episode per week)