This study was performed to compare the radiation dose and image quality of the cone beam CT and new low-dose MDCT protocols in assessment of maxillary sinus diseases. This was conducted by division of this research into two parts; first part: in-vitro study and second part: in-vivo study. The first part of this study was carried out in order to select the low-dose MDCT protocol using 16-MDCT scanner and CBCT protocol using i-CAT scanner that were used in the second part depending on radiation dose measurements and image quality assessments. Firstly, ten MDCT protocols were examined by changing the mAs and pitch factor starting from the standard MDCT protocol until the cutoff value of a non- diagnostic image quality was reached. Then, three CBCT protocols were examined by changing the mAs and voxel size until the best diagnostic image quality with an appropriate dose was obtained. The second part of the present study was conducted on thirty Egyptian patients (18 males and 12 females) with an age range between 10-40 years old and a mean age of 20.8±9.7 years. They were collected from Oral and Maxillofacial radiology and Oral Surgery Departments in Faculty of Oral and Dental Medicine and ENT Department in Al Kasr Al-Aini Faculty of Medicine, Cairo University, Radiology Department in Mahmoud Mosque Society, and Oral Surgery Department in Ahmed Maher Hospital. They were divided into two main groups: Study group: twenty patients were scanned by the new low-dose MDCT and CBCT protocols. Control group: ten patients were scanned by the standard MDCT protocol. Based on the results of the present study and with respect to the methodology it could be concluded that: 1-The new low-dose MDCT protocol is a viable method for maxillary sinus examinations that yields a diagnostic image quality for osseous and soft tissue details using an effective dose seven times lower than that of standard MDCT and one and a half times more than that of CBCT. 2-The parameters of the new low-dose MDCT protocol VIII are applicable for maxillary sinus disease examinations in adults, while the parameters of the new low-dose MDCT protocol IX are applicable for maxillary sinus disease examinations in children. 3-The CBCT scanner is an adequate method for screening purposes of the maxillary sinus diseases.