The purpose of this study was to investigate the prevalence and clinical correlates of apathy and depression in Parkinson disease (PD), and to clarify whether apathy can be dissociated from depression. One hundred fifty patients with PD completed the Beck Depression Inventory Second Edition (BDI-II), Starkstein's Apathy Scale (AS), and a quality of life (QOL) battery. Hoehn and Yahr (HY) staging, the Unified Parkinson's Disease Rating Scale (UPDRS), and the Mini-Mental State Examination (MMSE) were performed on the same day. Apathy (AS score > or = 16) was diagnosed in 60% of patients and depression (BDI-II score > or = 14) in 56%. Apathy coexisted with depression in 43% of patients, compared with depression without apathy in 13% and apathy without depression in 17%. Apathy scale score was significantly correlated with UPDRS scores, HY stage, and age, whereas BDI-II score was correlated only with UPDRS scores. Both AS and BDI-II scores were negatively correlated with QOL. However, multiple regression analysis revealed that depression was strongly and negatively associated with emotional well-being and communication, whereas apathy was mainly associated with cognition and stigma. These findings suggest that apathy and depression may be separable in PD, although both are common in patients with PD and are associated with QOL.