This comprehensive study aimed to evaluate motor and non-motor symptoms of Parkinson's disease (PD) and patients with a scan without evidence of dopaminergic deficit (SWEDD) using diffusion tensor imaging (DTI) metrics. The study included 156 PD, 36 SWEDD, and 68 healthy control (HC) subjects, extracting comprehensive demographic data, motor variables, and full-scale non-motor tests from the PPMI database. Additionally, the study incorporated DTI's fractional anisotropy metric across three Substantia Nigra (SN) subregions. The results indicated notable differences in depressed mood percentages among the groups, with SWEDD having the highest rate. Both PD and SWEDD groups exhibited significantly higher anxiety scores compared to HCs. PD patients showed a significantly higher prevalence of olfactory dysfunction, with individuals without rapid eye movement sleep behavior disorder (RBD) exhibiting greater fractional anisotropy (FA) values in the left middle SN region. The SWEDD group displayed higher FA in specific SN regions, particularly concerning olfactory dysfunction. These findings provide insight into the potential role of DTI imaging in forecasting PD's clinical progression, emphasizing the significance of motor and non-motor symptoms. This study contributes to our understanding of the disease's multifactorial nature, bridging the gap between imaging metrics and clinical symptoms. The results shed light on the potential of DTI in understanding the pathophysiological features of PD and SWEDD.