This study aimed to clarify associations between neuropsychological scales and regional cerebral blood flow (rCBF) of on ‍123I-IMP-SPECT in patients with Parkinson's disease with mild cognitive impairment (PD-MCI). Forty-two participants (mean age, 65.5 ± 8.9 years; mean disease duration, 11.1 ±5.7 years) were evaluated using the Wechsler Adult Intelligence Scale, third edition (WAIS-III), Wechsler Memory Scale, revised (WMS-R), Stroop test, Category word fluency, Auditory verbal learning test, Raven colored progressive matrices, Trail Making Test-B, and Clock drawing test. Participants were classified into PD-MCI and PD non-demented (PD-ND) using ten of these scales or its subtests. The rCBF of the posterior cingulate gyrus, precuneus, and parietal lobes was evaluated by ‍123I-IMP-SPECT using the easy Z-‍score imaging system (eZIS analysis). Extent was the extent index of voxels showing z-score > 2, and Severity was mean z-score in those regions on eZIS analysis. Cingulate island sign score (CIScore) was the ratio of integrated z-scores of the posterior cingulate gyrus to those of the posterior cortex.Twenty-three participants were diagnosed with PD-MCI (55%). The rCBF indices were significantly increased in the PD-MCI group compared to the PD-ND group (Extent: P = 0.047; CIScore: P = 0.006). These indices were significantly correlated with WAIS-III Processing Speed (Extent: P = 0.041, R = -0.317; Severity: P = 0.047, R = -0.309), Stroop effect (Extent: P = 0.003, R = 0.443; Severity: P = 0.004, R = 0.437), WMS-R Visual memory (Extent: P = 0.019, R = -0.361; Severity: P = 0.014, R = -0.375), and Delayed memory score (Extent: P = 0.005, R = -0.423; Severity: P = 0.044, R = -0.312). The rCBF indices showed no correlations with the number of impaired cognitive domains. Collectively, decreased posterior parietal area rCBF and lower scores on selective neuropsychological scales might be helpful to detect a transition period from PD-MCI to PD-D.