To determine the morphology of the lacrimal sac fossa and bony nasolacrimal duct using computed tomography for obtaining detailed anatomical understanding of the drainage system and utilizing these measurements in planning for dacryocystorhinostomy (DCR) and nasolacrimal duct (NLD) obstruction in normal southwest (SW) population of Iran. One-hundred-sixty-five cases referred for the diagnosis of neuro-ophthalmic conditions were retrospectively studied. Measurements of lacrimal sac fossa were taken on three anatomical sections (upper, middle, and lower planes) utilizing a digital caliper/protractor instrument. Lacrimal thickness and two measurements of maxillary bone thickness were taken at each plane—namely, the “midpoint thickness” and the “maximum thickness.” The anterior extent of the nasal mucosa and NLD width was also evaluated. The mean maximum thickness of the maxillary bone at the three anatomical planes of the lacrimal sac fossa was 4.07 mm, 4.78 mm, and 5.60 mm, respectively. The midpoint thickness of the maxillary bone at each plane was 2.38 mm, 1.99 mm, and 1.68 mm, respectively, in both sexs. The lacrimal bone thickness at each level was 0.76 mm, 0.69 mm, and 0.67 mm, respectively. The proportion of the lacrimal sac fossa comprising the lacrimal bone at lower plane was 43.57% and showed a positive correlation with age (P=0.01). The mean anteroposterior bony nasolacrimal diameter was 5.94 mm with no significant difference between patient sex and age. According to the results, its indicate that performing an osteotomy during DCR could be easier in the Iranian SW population compared to other ethnics.