Positron emission tomography (PET) using the tracer 18F-fluorodeoxyglucose (18F-FDG) and [18F] 9-fluoropropyl-(+)-dihydrotetrabenazine (18F-FP-DTBZ) is widely utilized to measure metabolic activity and dopaminergic integrity in neurodegenerative diseases such as Parkinson's disease (PD). Previous studies employing 18F-FDG PET have primarily focused on motor or non-motor symptoms, rather than the severity of PD. This study aimed to measure the glucose metabolism of 18F-FDG and the dopaminergic function of 18F-FP-DTBZ across various Hoehn-Yahr (H&Y) stages, analyzing the correlation between metabolic activity, dopaminergic function, and H&Y stages to monitor the severity of PD.The cross-sectional study recruited 78 PD patients in 3 groups of H&Y stages I, II, and III-V and 18 healthy control (HC) participants to undergo 18F-FDG and 18F-FP-DTBZ PET scans. Differences in cerebral metabolism and dopaminergic function between groups were evaluated using Student's t-test and Mann-Whitney U test. Moreover, Pearson correlation analysis was used to explore the association between cerebral metabolism, dopaminergic function, and H&Y stages in all patients.Patients with PD exhibited significant hypometabolic activity in the frontal cortex and relative hypermetabolic activity in the putamen, globus pallidus, thalamus, and cerebellum when compared to HC individuals (P<0.05). Further imaging-clinical correlation research depicted the negative correlation between the metabolic activity in the frontal and putamen regions with H&Y stage. Furthermore, the 18F-FP-DTBZ binding reductions were 18.6%, 46.6%, and 56.9% for the caudate, anterior putamen, and posterior putamen at H&Y stages I; 36.0%, 56.9%, and 65.9% at H&Y stages II; and 41.2%, 61.9%, and 68.5% at H&Y stages III-V, respectively. The 18F-FP-DTBZ binding of caudate, anterior putamen, and posterior putamen exhibited significantly negative correlations to H&Y stage.In PD, 18F-FDG and 18F-FP-DTBZ PET imaging represent potential biomarkers for tracking metabolic activity and dopaminergic degeneration, offering valuable insights into estimating the severity of disease.Copyright © 2025 AME Publishing Company. All rights reserved.