Introduction Isolated nasal obstruction (INO) is a common complaint of multiple etiology. The preoperative evaluation of patients presenting with nasal obstruction and deviated nasal septum (DNS) does not typically include imaging. The benefits of performing computed tomography (CT) in the preoperative setting are inconclusive. Objective Assessing the contribution of preoperative CT to the surgical treatment of non-sinusitis patients presenting with INO and DNS. Methods A retrospective cohort study on patients referred to surgery for nasal obstruction due to DNS or turbinate hypertrophy between 2006 and 2015. Data was retrieved from patients' medical charts. The CT scans and clinical data were reassessed by a second surgeon blinded to the patients' clinical course. Results Seventy of the 843 patients (8.06%) who underwent endoscopic sinonasal procedures during the study period had presented with INO and met the inclusion criteria. Thirty-eight (55.88%) of them underwent CT scans during their preoperative assessment. Modification of the initial preoperative planning based on the radiological findings was required in 32 cases (84.2%). When reassessed by a second blinded surgeon, 58% of cases required surgical modification rather than classical submucosal resection of nasal septum and turbinate reduction (P = 0.048). Conclusion Computed tomography was found beneficial in the preoperative planning for patients with INO. The original surgical plan based upon physical examination findings was modified based on radiological findings in 84.2% of the patients.