Dementia is the most common risk factor for delirium in the elderly. Here we will review the evidence that proposed pathogenetic mechanisms for delirium (such as reduced cerebral metabolism, imbalance of the noradrenergic/cholinergic neurotransmission, inflammation, disturbances in neuronal systems which regulate stress and the sleep/wake cycle) are also a part of the pathophysiology of Alzheimer's disease. In particular, the role of inflammatory mechanisms in both disorders will be discussed.