Aim: Slow colonic transit time (CTT) and pelvic floor dyssynergia (PFD) are major contributors to constipation in patients with Parkinson's disease (PD). However, no symptom survey yet exists that effectively differentiates the contributing aetiologies. The significance of individual pelvic floor musculature behaviours and their relationship with colorectal dysmotility in constipated patients with PD are still controversial and need further clarification. We aimed to investigate how differentiated constipation-related symptoms of PD patients with constipation may identify constipation groupings and to register the pathophysiological features of the pelvic musculature. Method: Our subjects undertook CTT, defaecography and the Knowles-Eccersley-Scott Symptom questionnaire. The pathological aetiologies were categorized as group 1 (slow CTT) and/or group 2 (puborectalis syndrome) and/or group 3 (pubococcygeus syndrome), in accordance with the CTT and defaecography results. Results: Constipation-related symptoms such as incomplete evacuation and defaecation difficulty yielded high post-test probabilities (81% and 88%, respectively) in groups 3 and 2, but a low post-test probability in group 1 (58%). Changes in the anorectal angle and perineum descent during straining were significantly correlated with CTT (r = 0.57 and r = 0.61, respectively) and with each other (r = 0.82). Conclusion: Our findings that neural control of the puborectalis and pubococcygeus, along with colorectal peristalsis, were in a similar state of degeneration is key information that should assist physicians to instigate more effective management for colonic dysmotility or PFD.