This study addressed whether cardiac sympathetic denervation progresses over time in Parkinson's disease. In 9 patients without orthostatic hypotension, 6‐[¹⁸F]fluorodopamine positron emission tomography scanning was repeated after a mean of 2 years from the first scan. 6‐[¹⁸F]fluorodopamine‐derived radioactivity was less in the second scan than in the first scan, by 31% in the left ventricular free wall and 16% in the septum. In Parkinson's disease, loss of cardiac sympathetic denervation progresses in a pattern of loss suggesting a dying‐back mechanism.