Few studies have compared neuropsychiatric disorders and functional abilities in the early stage of DLB and AD and their influence on caregiver distress. The aim of this study is to assess neuropsychiatric disorders, functional abilities and caregiver distress in DLB and in AD subjects. Sixteen subjects affected by probable DLB and 12 subjects affected by probable AD were enrolled. All subjects underwent a wide neuropsychological examination. Caregiver's distress was also assessed. Subjects affected by DLB performed better in long-term memory tests, whereas AD subjects performed better in attentive and executive function tests. The Neuropsychiatric Inventory (NPI) total score was significantly higher in DLB subjects than in AD subjects. Furthermore, DLB subjects scored worse than AD subjects in both Activities of Daily Living scale (ADL) and Instrumental Activities of Daily Living scale (IADL) scales. Overall caregiver distress was higher in DLB than in AD subjects. High distress was observed in DLB caregivers alone and was caused by delusion, hallucinations, anxiety and apathy. DLB subjects have a different neuropsychological profile, more psychiatric symptoms and more serious functional deficits than AD subjects in the early cognitive decline, furthermore DLB caregivers are more stressed than AD caregivers.