Objective: To investigate the reason for fungal balls (FBs) being localized in paranasal sinuses, we analyzed the clinical presentations of patients with FB rhinosinusitis (FBS). Methods: Clinical data, anatomical variation (ie, nasal septal deviation, concha bullosa, and Haller cell), as well as measurements of nasal resistance (NR), nasal cavity volume (NCV), and nasal cross-sectional area (NCA) using active anterior rhinomanometry and acoustic rhinometry were collected from FBS patients hospitalized in our hospital between January 2021 and December 2022. A retrospective analysis was conducted using IBM SPSS 19.0 to perform the Shapiro–Wilk test, t-test and logistic regression analysis. Results: A total of 95 FBS patients, including 33 male and 62 female patients, were included in this study. FBs in maxillary sinus were the most common (83, 87.4%), followed by sphenoid sinus (9, 9.5%). Logistic multivariate regression analysis revealed that a higher left-to-right NR ratio was associated with an increased likelihood of FBs being present in the left sinus [Odds ratios (OR) = 0.185; 95% CI, 0.061-0.558; P < .01]. When the ratio of the left-to-right second-minimum NCA was higher and the FB was more in the right sinus (OR = 3.194; 95% CI, 1.593-6.405; P = .001). Additionally, when the difference between left and right NCV was greater and FB occurred more commonly in the right sinus (OR = 1.435; 95% CI, 1.196-1.721; P < .001). Nonetheless, the presence of nasal septum deviation and concha bullosa did not significantly contribute to FB formation. Conclusions and significance: The differences in NR, NCA, and NCV between the affected and unaffected sides of nasal cavity are risk factors for the FB formation. To reduce FBS recurrence, it is important to focus on improving nasal ventilation during the surgical treatment.