Anosmia following head trauma is relatively common and in many cases is persistent and irreversible. The ability to objectively measure such a decline in smelling, for both clinical and medicolegal goals, is very important. The aim of this study was to find results of brain Single Photon Emission Computed Tomography (SPECT) in anosmic subjects after closed head trauma. This case-control cross sectional study was conducted in a tertiary referral University Hospital. The brain perfusion state of nineteen anosmic patients and thirteen normal controls was evaluated by means of the SPECT with 99mtc- ECD infusion- before and after olfactory stimulation. The orbitofrontal lobe of the brain was assumed as the region of interest and changes in perfusion of this area before and after the stimulations were compared in two groups. The mean of brain perfusion in controls before and after the stimulation was 8.26% ± 0.19% and 9.89% ± 0.54%, respectively (P < 0.0001). Among patients group, these quantities were 7.97% ± 1.05% and 8.49% ± 1.5%, respectively (P < 0.004). The difference between all the measures in cases and controls were statistically significant (P < 0.0001). There were no differences in age and sex between two groups. The brain SPECT is an objective technique suitable for evaluating anosmia following the head trauma and it may be used with other diagnostic modalities.