Objectives: The olfactory bulb (OB) plays a pivotal role in the processing of olfactory information. The aim of this study was to investigate the OB volume changes and its possible associations with nasal septal deviation. Study Design: Cross-sectional study. Setting: Otolaryngology Department of Bozok University School of Medicine and Neurology Department of Yozgat State Hospital. Subjects and Methods: Ninety patient's cranial magnetic resonance imaging (MRI) studies (46 males and 44 females, mean age 36 +/- 13.4 years; range 18-56 years) with isolated nasal septal deviations were recruited for the study. Olfactory bulb volumes in all study subjects were evaluated in T2-weighted coronal MRI images by planimetric manual contouring. Results: Nasal septal deviation angles were found to range between 5 degrees and 23.21 degrees (mean 13.6 degrees +/- 3.58 degrees). The right-sided deviations included 17 mild (<9 degrees, Group I), 20 moderate (9 degrees-15 degrees, Group II), and 16 severe (15 degrees and up, Group III) patients. The left-sided deviations included 14 mild (<9 degrees, Group I), 13 moderate (9 degrees-15 degrees, Group II), and 10 severe (15 degrees and up, Group III) subjects. Olfactory bulb volumes were calculated in both right-and left-sided deviation groups. In the patients with left-sided septal deviations of Groups I, II, and III, the left OB volumes of Groups I, II, and III were 46.49 +/- 3.87, 47.46 +/- 3.36, and 60.68 +/- 5.65 mm(3) and the right OB volumes were 53.37 +/- 3.76, 56.47 +/- 4.43, and 76.69 +/- 6.84 mm(3), respectively. The statistical evaluation of the right OB volumes did not produce significant difference between Groups I and II (P = 0.73). The authors demonstrated statistically significant differences in comparison of Groups I to III and Groups II to III (P = 0.002 and P = 0.016, respectively). In the right septal deviation group for Groups I, II, and III, mean volumes of right OB volumes were 45.59 +/- 4.46, 48.63 +/- 3.78, and 61.35 +/- 5.84 mm(3), respectively, and the left OB volumes were 54.67 +/- 4.73, 57.65 +/- 4.53, and 75.84 +/- 7.67 mm(3), respectively. There was no statistically significant difference between Groups I and II (P = 0.95) left OB volumes in the right-sided deviation group, but statistically significant difference was demonstrated in Groups I to III and Groups II to III compartments (P = 0.002 and P = 0.003). Conclusion: In our study, while mild and moderate septal deviations lacked any significant affect on OB volumes, severe deviations were found to have significant impact on these parameter. Additionally the contralateral OB volumes in the severe septum deviation group were significantly bigger when compared to the ipsilateral OB volumes. Further multidisciplinary studies are required to evaluate the clinical significance of OB volume changes in diagnosis and follow-up of several otolaryngologic or nonotolaryngologic diseases.