Rhinosinusitis disorders are often associated with Cystic Fibrosis. They can restrict quality of life enormously and give cause to repeated ENT surgery. The basic defect in CF is a dysfunction of chloride channels in exocrine glands, leading to retention of secretions and consecutive chronic inflammation with bacterial superinfections.

The prospective placebo controlled cross-over study aims at the evaluation of a nasally inhalation of Pulmozyme with respect to mucus retention and resulting inflammation.

Inclusion Criteria:

• Subject has a confirmed diagnosis of cystic fibrosis based on: 3 positive sweat chloride tests and/or genetic characterisation
• Subject is 5 years of age or older
• Subject has chronic or recurrent rhinosinusitic disorders
• Subject is able to comply with the procedures scheduled in the protocol
• Women of childbearing potential are only included into the study, if they are using an effective method of birth control during the protocol (e.g. implants, combined oral contraceptives, injectables, some IUDs, sexual abstinence or vasectomised partner)

Exclusion Criteria:

• Subject has a critical condition defined as: FEV1 < 30% and / or SaO2 < 93% without O2-substitution; need of O2-substitution
• Subject had an ENT surgery within 6 months prior to study
• Subject shows signs of nasal bleeding
• Subject has an ear drum perforation
• Subject had an acute rhinosinusitis or a pulmonary exacerbation at study entry with need of additional systemic antibiotic therapy
• Subject has a new therapy with nasal topic steroids during treatment interval
• Subject has a new systemic steroid therapy
• Subject is unlikely to comply with the procedures scheduled in the protocol
• Subject has a known allergic reaction to the medication
• Subject is pregnant or breastfeeding
• Patient participates in another clinical trial within 30 days prior to study entry or 30 days after end of the study.