Objective: Dementia and cognitive impairment (CI) are common in Parkinson's disease (PD) and have important clinical consequences. We explored the prognostic factors for CI in patients with PD. Methods: A total of 102 patients with PD in Xuan wu hospital and Qian dongnan People's Hospital from 2005 to 2010 were included in this study. All patients underwent clinical and neurological assessments. Relevant demographic and performance parameters were analysed to determine variables that may be independently associated with the progression of CI. Results: In the 6-month follow-up group, CI progressed in three out of 58 cases (5%): two cases progressed from mild CI (MiCI) to moderate CI (MoCI), and one case from MoCI to dementia. In the six-month-to-two-year follow-up group, seven out of 46 cases (15%) worsened: one case developed MiCI, three cases progressed from MiCI to MoCI and three other cases from MoCI to dementia. In the two-to-five-year group, 20 out of 44 cases (45%) worsened with one case developing MiCI, 14 cases progressing from MiCi to MoCI and five cases from MoCI to dementia. Compared with other patients, those with worsening of CI symptoms were significantly older in the two-to-five-year group. Progression of CI was also associated with age at onset and initial staging of PD. Conclusions: Advanced age, late onset of disease and severity of PD are the predictive factors for the progression of CI in PD. The highest probability of progression of CI is in patients with initial severe impairments of visuospatial function.