Background: Looking in literature reveals that aging is accompanied by olfactory dysfunction and hyposmia/anosmia is a common manifestation in some neurodegenerative disorders. Olfactory dysfunction is regarded as non-motor manifestations of Parkinson disease (PD). The main goal of this study was to examine the extent of olfactory dysfunction in Persian PD patients.Methods:We used seven types of odors including rosewater, mint, lemon, garlic which were produced by Barij Essence Company in Iran. Additionally, coffee and vinegar were used. Subjects had to distinguish and name between seven previously named odors, stimuli were administered to each nostril separately.Results:Totally, 92 patients and 40 controls were recruited. The mean (standard deviation) (SD) age patients was 64.88 (11.30) versus 61.05 (7.93) in controls. The male: female ratio in patients was 50:42 versus 22:18 in control group. Also, mean UPDRS score (SD) in patients was 24.42 (5.08) and the disease duration (SD) was 3.72 (3.53). Regarding the number of truly detected odors, there were a significant higher number of correct identified odors in control group in comparison with the PD patients. Furthermore, there was a significant negative correlation between number of correct diagnosed smells and UPDRS (Pearson Correlation= -0.27, P = 0.009); conversely, no significant correlation between the duration of Parkinson disease and number of correct diagnosed smells (P > 0.05).Conclusion: Smelling dysfunction is a major problem in Persian PD patients and it requires vigilant investigation for the cause of olfactory dysfunction exclusively in elder group and looking for possible PD disease.