Abstract: Accurate nursing assessment is a critical element in the identification of health problems and treatment strategies for older adults who have delirium and/or dementia. This practice update provides information on the differentiation between these two debilitating and adverse health events, along with some useful assessment frameworks and other resources. Comments from people with delirium and dementia are interspersed throughout the article to draw attention to the impact of these conditions on people's lives and well-being. The article includes the 'A presenting concern framework', useful mnemonic devices to help nurses assess an older person who may have delirium or dementia, and a list of online resources.