We evaluated 109 Chinese patients with Parkinson's disease (PD) in three ways: using a standardized psychiatric interview for depression and anxiety, using standardized neurological evaluation for motor disability, and using cognitive assessment for cognitive impairment. Six of the 109 patients who had dementia and another two afflicted with organic delusional disorder were excluded from further analysis. The remaining 101 PD patients were divided into the following three groups according to the DSM-III-R criteria: major depressive disorder (n = 18), other depressive disorders (n = 25) including dysthymic disorder and depressive disorder not otherwise specified, and no depression (n = 58). The frequency of major depressive disorder of the 109 PD patients was 16.5%, and the frequency of major and other depressive disorders, taken together, was 42.2%. Using the percentage points measured on the Schwab & England Activities of Daily Living Scale as the dependent variable to fit a multivariate regression model, we found the lower score significantly correlated with the diagnosis of depressive disorder and higher score of the Hamilton Depression Rating Scale, in addition to motor disability and disease severity of PD. Given the high frequency of depression and the significant correlation between depression and performance in daily functional activites, we believe that an evaluation of PD patients for coexisting depression is necessary for a better therapeutic outcome.