Constipation is frequently reported in Parkinson's disease (PD). We evaluated the characteristics of patients with PD and constipation and explored the role of T cell subsets in PD-associated constipation. One hundred and two patients with PD treated at the First Affiliated Hospital of Bengbu Medical College were enrolled in this study between January 2012 and October 2013. All patients completed KESS questionnaires and constipation was rated. The proportions of peripheral blood Thl7 and Treg cells were assessed by flow cytometry in 45 patients. Colonoscopies were performed in six patients. Thirty-one patients with PD reported slow-transit constipation (STC), 15 rectal evacuation disorder (RED) and 33 mixed constipation (Mixed). STC most frequently occurred before onset of PD motor symptoms, while Mixed occurred before or after motor symptoms, and RED occurred most frequently after motor symptoms. CD4+ T cell infiltration in the colonic mucosa was observed in patients with PD and constipation. The frequency of Th17 and Treg cells in patients with PD and constipation was significantly higher than in those without constipation (P<0.001). Among patients with PD and constipation, the frequency of Th17 and Treg cells in STC was the highest. However, there was no difference in the ratio of Th17/Tregs between the patients with PD with and without constipation, or patients with PD and different types of constipations (P>0.05). Constipation reported before the onset of PD motor symptoms was most often STC or Mixed, and PD constipation may be associated with immune activation in the colonic mucosa.