Background: To examine whether combined use of I-123-FP-CIT dopamine transporter single photon emission computed tomography (DAT-SPECT) and I-123-MIBG myocardial scintigraphy (MIBG) is superior to either modality alone for diagnosing Parkinson's disease (PD). Methods: Patients with probable PD (n = 120) who underwent both DAT-SPECT and MIBG myocardial scintigraphy within short intervals were enrolled. Specific binding ratio (SBR) of DAT-SPECT images and heart-to-mediastinum (H/M) ratio of MIBG images were used as quantitative measures. We classified patients into 4 groups based on SBR value and H/M ratio, or into two groups based on the striatal asymmetry index (SAI) of DAT-SPECT, and examined the clinical features of each group. We also investigated the characteristics of SWEDDs (scans without evidence of dopaminergic deficits) patients. Finally, we calculated the sensitivity and specificity of each method and the combined method. Results: SBR value was significantly correlated with both early and delayed H/M ratio values. Motor complications and hallucinations were observed at high frequency in the group with both lower SBR and H/M ratio, and hallucinations appeared in the group with larger SAL SWEDDs were observed 8.3% of patients. The sensitivity and specificity of diagnosing PD were 91.7% and 15.0% by SBR of DAT-SPECT, 78.3% and 90.0% by H/M ratio of MIBG uptake, and 74.2% and 95.0% by the combined modalities, respectively. Conclusions: Combined use of DAT-SPECT and MIBG myocardial scintigraphy increases the specificity of PD diagnosis, and is helpful for understanding the clinical features or predicting complications. (C) 2017 Elsevier B.V. All rights reserved.