AIM: Mild cognitive impairment (MCI) is common in Parkinson's disease (PD). This study compared cerebral metabolism and dopaminergic function in PD patients with MCI (PD-MCI) versus those with normal cognition (PD-NC) and healthy controls (HC). MATERIAL AND METHODS: A total of 78 PD patients (40 PD-MCI, 38 PD-NC) and 28 HC underwent F-18-fluorodeoxyglucose positron emission tomography (F-18-FDG PET) (metabolism) and [F-18] 9-fluoropropyl-(+)-dihydrotetrabenazine (F-18-FP-DTBZ) PET (dopaminergic vesicular transporter). Group comparisons used t-tests. Correlations between PET measures and cognitive scores (MMSE, MoCA) were assessed. RESULTS: PD-MCI patients showed significantly reduced FDG uptake in frontal and parietal regions compared to PD-NC (P=0.0 03, P=0.025). PD-MCI also exhibited lower F-18-FP-DTBZ binding, particularly in bilateral caudate (contralateral P=0.018; ipsilateral P=0.048). In PD patients, FDG uptake in frontal/parietal lobes and F-18-FP-DTBZ uptake in caudate and putamen positively correlated with MMSE and MoCA scores (all P<0.05). CONCLUSION: Striatal dopamine depletion and hypometabolism in frontal/parietal regions are associated with cognitive deficits in PD-MCI patients. (c) 2025 The Royal College of Radiologists. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.