rhinosinusitis, though only when sign and symptoms suggest complications. In this scenario orbits, skull base, anterior and central skull base require even more meticulous assessment than sinus cavities; contrast administration is mandatory, particularly to detect intracranial lesions. On the other hand, the role of CT is much more extensive in chronic rhinosinusitis, both to indicate the need for endoscopic sinus surgery and to plan the most proper strategy. Thorough knowledge of the anatomy of sinuses and mucus drainage pathways is the key to interpret CT findings. A centrifugal approach is normally used in reporting, assessing nasal fossae and drainage conduits first, and only ultimately moving to the periphery, i.e. sinus cavities, the involvement of which is quite often only a secondary effect. After surgery, CT scan may be indicated if major signs and symptoms (nasal obstruction, pus drainage, facial pain) persist. Sinus anatomy may be significantly altered, althoughas a general rule -it is simplified; however, interpretation of CT images is relatively easy if the main (and most commonly used) procedures performed are known by the radiologist. The main goals of imaging are the detection of any residual sign of mucosal inflammation along the surgically widened mucus drainage pathways, as well as the identification of retention mucocele or infectious complications. There is a great variety of sinonasal tumours due to the many different tissue types present within the maxillofacial complex. Benign lesions may be of epithelial origin, but also fibro-osseous or vascular lesions do occur. Squamous cell carcinoma is the most common malignancy of the sinonasal area, but other tumours may originate from glandular tissue (e.g. adenocarcinoma) or neural crest cells (e.g. aesthesioneuroblastoma or melanoma). Only few of them show typical imaging features. The main goal of imaging is to evaluate tumour extent and guide treatment planning. In this lecture, imaging patterns of sinonasal tumours will be shown. The current TNM classification for malignant tumours will be discussed and illustrated. Ultrasonography (US) is a readily available non-invasive technique that can be used for the detection of a soft tissue mass. It gives a first impression of the size, location in relation to the fascia and consistency of soft tissue lesions. An important ability of US is the potential to differentiate between cystic and solid lesions; however, specificity in further characterising a soft tissue mass is low. MR is the next imaging modality to perform for the evaluation of soft tissue lesions. MR is accurate in determining size, confinement to or extension beyond the anatomic compartment of origin and the relationship to the neurovascular bundle and adjacent bone and joints. Although histopathological examination remains the gold standard, differentiation between malignant and benign soft tissue masses, indication of the grade of malignancy and prediction of the histological diagnosis are challenging goals of MR imaging. As such, characterisation of soft tissue masses starts with interpretation of signal characteristics on T1-and T2-weighted sequences. Combinations of signal intensities reveal the different tumour components (e.g. fat, water, and blood), and thus provide indirect information about the nature of soft tissue masses. Additional imaging parameters combined with clinical parameters such as age, gender, etc.