The objective of this paper is to study the incidence of septa in the maxillary sinus and measure the height of the underlying alveolar process using panoramic radiography and computerized tomography (CT scans). Thirty patients who were going to be treated with dental implants were submitted to panoramic radiographs and CT scans. Sixty maxillary sinuses were analysed and divided into 2 groups: group 1 (totally edentulous) and group 2 (partially edentulous). The sinuses were divided into 3 regions (anterior, middle, and posterior), the septa were analysed, and the heights of the alveolar processes were calculated in these 3 areas. Of the 30 patients, 36.5% had maxillary sinuses, and 25% of these sinuses had septa, and 11.8% of the panoramic radiographs were false-negatives. In the panoramic radiographs of 10 patients, 3 had bilateral septa, 5 had a septum in only one sinus, and 2 patients had 2 unilateral septa. In the CT scans of 11 patients, 4 patients had a bilateral septa, 5 had a septum in only 1 sinus, and 2 patients had 2 unilateral septa. Therefore, 2 more septa were observed in the CT scans. In the study of the height of the subantral alveolar process, the least amount of difference between both techniques occurred in the middle region of the sinus. The CT scan is more reliable than the panoramic radiograph in diagnosing maxillary septa because of its greater accuracy. In the panoramic radiograph, the middle portion of the alveolar process in the posterior subantral segment was the least distorted of the three portions measured.