Background: Anatomical variants of the paranasal sinuses and nasal cavity are common findings in computed tomography (CT) imaging and play a crucial role in the clinical presentation and management of sinonasal diseases. These variants can impact surgical planning, particularly in functional endoscopic sinus surgery (FESS). Aim: This study aims to evaluate the incidence of anatomical variants in the paranasal sinuses and nasal cavity among the South Indian population and to assess their significance in surgical planning. Methods: CT scans of 234 patients, including those with minimal and significant sinonasal disease, were reviewed. Anatomical variants were identified and categorized, with their prevalence calculated. The association between these variants and the severity of sinonasal disease was analyzed. Statistical analysis was accomplished using SPSS version 23.0. Results: The most common anatomical variants observed were deviated nasal septum (66.7%), concha bullosa (56.4%), and Haller cells (33.3%). Significant associations were found between the prevalence of these variants and the severity of sinonasal disease. Concha bullosa was present in 100% of patients with significant sinonasal disease, with bilateral variants being more prevalent in this group. The findings suggest that specific anatomical variants, particularly when bilateral, are strongly associated with more severe sinonasal disease. Conclusion: This study highlights the high prevalence of anatomical variants in the South Indian population and their significant association with sinonasal disease severity. These findings underscore the importance of detailed preoperative imaging and assessment to inform surgical planning, potentially improving surgical outcomes. Recommendations: Further studies are recommended to explore the impact of these anatomical variants on surgical outcomes and to develop population-specific guidelines for preoperative assessment and management in sinonasal surgery.