ObjectiveEvaluation of the correlation between18F-fluorodeoxyglucose-positron emission tomography (18F-FDG PET) and cognitive function in first-diagnosed and untreated Parkinson’s disease (PD) patients.Materials and methodThis cross-sectional study included 84 first diagnosed and untreated PD patients. The individuals were diagnosed by movement disorder experts based on the 2015 MDS Parkinson’s disease diagnostic criteria. The patients also underwent18F-FDG PET scans and clinical feature assessments including the Montreal Cognitive Assessment (MoCA) scale. Glucose metabolism rates were measured in 26 brain regions using region of interest (ROI) and pixel-wise analyses with displayedZscores. The cognitive function was assessed by professionals using the MoCA scale, which covers five cognitive domains. Spearman’s linear correlation and linear regression models were used to compare the correlations between18F-FDG metabolism in each brain region and cognitive domain, using SPSS 25.0 software.ResultThe results indicated a positive correlation between executive function and glucose metabolism in the lateral prefrontal cortex of the left hemisphere (p= 0.041). Additionally, a positive correlation between memory function and glucose metabolism in the right precuneus (p= 0.014), right lateral occipital cortex (p= 0.017), left lateral occipital cortex (p= 0.031), left primary visual cortex (p= 0.008), and right medial temporal cortex (p= 0.046). Further regression analysis showed that for every one-point decrease in the memory score, the glucose metabolism in the right precuneus would decrease by 0.3 (B= 0.30,p= 0.005), the glucose metabolism in the left primary visual cortex would decrease by 0.25 (B= 0.25,p= 0.040), the glucose metabolism in the right lateral occipital cortex would decrease by 0.38 (B= 0.38,p= 0.012), and the glucose metabolism in the left lateral occipital cortex would decrease by 0.32 (B= 0.32,p= 0.045).ConclusionThis study indicated that cognitive impairment in PD patients mainly manifests as changes in executive function, visual-spatial function and memory functions, while glucose metabolism mainly decreases in the frontal and posterior cortex. Further analysis shows that executive function is related to glucose metabolism in the left lateral prefrontal cortex. On the other hand, memory ability involves changes in glucose metabolism in a more extensive brain region. This suggests that cognitive function assessment can indirectly reflect the level of glucose metabolism in the relevant brain regions.