An expert group of the European Academy of Allergy and Clinical Immunology (EAACI) and the European Rhinologic Society (ERS) has recently published the revised position paper for acute and chronic rhinosinusitis (EPOS 2012). In the following article, the most important aspects of the EPOS 2012 paper concerning chronic rhinosinusitis (CRS) are referenced. Every 10th European is suffering from a chronic inflammation of the nose and paranasal sinuses.2 EPOS key messages according CRS are: 1. CRS is an inflammatory disease, not an infection. 2. CRS comes in 2 different subtypes, namely CRS without polyps (CRSsNP) and CRS with polyps (CRSwNP). CRSwNP is diagnosed, when nasal polyps are visible at an appropriate nasal endoscopic examination. Otherwise CRSsNP is classified. In the EPOS 2012 paper the current pathogenetic knowledge of these 2 different CRS subtypes are discussed. Current research focuses on epithelial/immune cell interactions, the biofilm hypothesis and the superantigen hypothesis. Both CRS subtypes may be associated with different frequencies with other diseases, especially allergies, asthma and aspirin exacerbated respiratory disease (AERD). These comorbidities should be recorded and treated. The standard diagnostic procedures include medical history, nasal endoscopy, CT-scans of the paranasal sinus, and allergy test of common inhalant allergens. The classification of disease severity in mild, moderate and severe was complemented with a concept of symptom control in controlled, partly controlled and uncontrolled. Also, a 'difficult-to-treat-CRS' was defined. The choice of therapy depends upon symptom intensity. In patients with moderate and severe symptoms, usually several weeks of conservative treatment including topical steroids are administered. In non-responders, surgical treatment (functional endonasal sinus surgery) is indicated. The EPOS Group offers evidence-based treatment algorithms for general practitioners and ENT-specialists.