Several articles have been written about hyper inflated sinus structures. Never before, however, a complete overview of all possible pressure induced variations of sinus anatomy have been published. The aim of this study was to make an inventory of the most common CT signs of hyper inflated paranasal sinus structures. During a period of 2 years all CT-scans of the paranasal sinuses made in an ENT-department were studied and the most typical shapes of hyper inflated sinus structures were recorded. The authors documented 9 different anomalies of the anterior paranasal sinus complex (frontal sinus, frontal and supra-orbital recess and anterior ethmoid), 8 of the ethmoid and 1 of the sphenoidal sinus. These hyper inflated paranasal sinus structures can only be generated by high positive intranasal pressures. The nose blowing manoeuvre is the only manoeuvre that generates extremely high pressures and as such it might be the driving force in the generation of these hyper inflated paranasal structures and consequently play a role in the pathophysiology of chronic sinusitis. Pneumatisation of the sinuses starts at birth and is a lifelong process. Sometimes, however, pneumatisation can be extreme and will result in facial deformities. Pneumosinus dilatans, is such a condition, characterized by an abnormal dilatation of a paranasal sinus cavity, containing air only. Most reports describe pneumosinus dilatans of the frontal sinus, but also other sinuses can show this phenomenon: maxillary sinus and in one case a unilateral pneumosinus dilatans of nearly all sinuses (maxillary, ethmoid, and sphenoid sinus) was described. Recently Kalavagunta et al., described a less dramatic expansion of the maxillary sinus and named it “Extensive Maxillary Sinus Pneumatisation” (EMSP). They were surprised to see that EMSP has received little attention in the literature. Neuner et al., described 9 different atypical pneumatisation abnormalities of the paranasal sinus anatomy. Most of deformities of the sinus pneumatisation are growth deformities of the thick bones that make up the frame of the sinuses. Only a few articles, deal with specific deformities of thinner bone structures such as “wavy orbital floor” and “frontal cells”. Never before, however, an article was published that studied all possible deformities due to increased pressures and tried to make a classification. So the aim of this study was to make an inventory of the most obvious pressures related deformities that can be seen on CT-scans of patients with rhinosinusitis.