Introduction : The respiratory functions have wide effects on the orthodontic diagnosis and the treatment planning, besides their effects on the stability of the treatment results. So it is important to have a better and more deeply analysis of the upper airway morphology, and to evaluate its relationship with the cephalometric features that determine the intermaxillary relationship . Objective: The aim of this study was to evaluate the relationship of the size and areas of the upper airways in adults to the sagittal intermaxillary relationship using sagittal and axial slices of three dimensional computed tomography. Materials and methods: The Sample's consisted of 29 adults (12males,17 females) selected from patients who were ordinary undergoing 3DCT for non-orthodontic nor otolaryngology purposes and didn’t have orthodontic treatment . the anteroposterior positions of both the maxilla and the mandible were evaluated with the ANB angle , AF-BF distance and Wits appraisal .Then Pearson's Correlation was calculated to investigate the possible relationship between the upper airway measurements and the Cephalometric measurements determining intermaxillary relationship at the sagittal plane. Results: We found statistically significant correlation between the upper airway measurements and the cephalometric measurements determining sagittal intermaxillary relationship. The depth and area of NA showed negative correlation with ANB ,WITS,AF-BF (p＜0.05). We noticed that females have statistically significant smaller oropharyngeal depth than males. Conclusions: There is a statistically significant correlation between the upper airway measurements and the cephalometric measurements determining the sagittal intermaxillary relationship in adults with no clinical symptoms of the upper airway disorders..