In the past some attempts have been made to study comparative anatomy of the Para nasal air sinuses. Among them some have made efforts to measure the dimensions of these Para nasal air sinuses. Mostly all of study was done on the dry bones in early phase and then with X-rays. As these dimensions are very important to the ENT surgeons and to the neurosurgeon to understand the normal anatomy of these PNS. So, in present study efforts have made to measure the dimensions of sphenoidal air sinus with the help of CT scan and MRI, Which are the latest modalities, which can give more accurate measurements. Here 50 CT scans of PNS of normal adults (37 males & 13 females) at J.J. Hospital radiology department, Byculla, Mumbai were studied. And MRI of Brain including PNS of 100 normal adults (50 males, 50 females) at Breach Candy Hospital, Mumbai was studied.

Key words: Para nasal air sinus (PNS), Antero posterior (A-P), Transverse (Trans.), Vertical (Vert.), CT scans, MRI.