Olfactory deficit is known to occur frequently in Parkinson's disease (PD). This study aimed to explore olfactory deficit in PD and to investigate its possible correlation with the disease severity or the depth of the olfactory sulcus. Fifty-nine PD patients and 25 normal controls were examined by the odor identification test with the crosscultural smell identification test (CC-SIT). Among these subjects, the depth of the olfactory sulcus of 42 PD patients and 8 controls was measured in the plane of the posterior tangent through the eyeballs using the coronal view brain MRI. The CC-SIT scores of the PD patients were significantly lower than those of the normal control (P<0.001). However, CC-SIT did not correlate with the disease duration, H-Y stage, score of UPDRS Part III, or the depth of either side of the olfactory sulcus (P>0.05). Our study confirms that CC-SIT is a helpful test in detecting the olfactory deficit in Korean PD patients. The absence of correlation of olfactory deficit with the disease severity or the depth of olfactory sulcus may suggest that olfactory loss precede the development of motor signs and not be a primary consequence of damage to the olfactory sulcus.