We compared caregiver burden in Parkinson disease with dementia (PDD) to that in Alzheimer disease (AD) and examined the factors contributing to the burden in PDD. Totally, 42 patients with PDD and 109 patients with AD and their caregivers participated in this study. The caregiver burden was measured using the Burden Interview (BI). Scores of Barthel activities of daily living (BADLs), Mini-Mental State Examination, Clinical Dementia Rating of patients, and score of Center for Epidemiologic Studies Depression scale, and Euro-quality of life of the caregivers were examined. The Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn and Yahr stage of the patients were administered to assess burden relating to parkinsonism on PDD. We used multiple linear regression to assess the predictors. The BI of caregivers was higher in PDD (47.9, Standard deviation [SD]: 3.8) than in AD (36.3, SD:2.1). In the AD group, the BI was predicted by cognitive function ((β±SE: -0.8±0.4, P value=04) and basic ADL status of patients (β±SE: -1.3±0.1, P<.001), depressive symptoms (β±SE: 1.1±0.1, P<.001), and poor quality of life (β±SE: -0.2±0.1, P=.017) in caregivers. In PDD group, BI was predicted only by scores of Part 1 on the UPDRS (β±SE: 2.9±1.3, P=.03) of patients and depressive symptoms (β±SE: 1.1±0.2, P<.001) of the caregivers. We concluded the caregiver burden is higher in PDD than in AD and factors predicting burden are different in AD and PDD. In patients with PDD, the neuropsychiatric problems are the major contributor to caregiver burden.