Although dementia is primarily considered a memory disorder, there are significant neuropsychiatric manifestations sufficient to cause decline in ability to carry out social or occupational functioning independently. Depressive symptoms are extremely common in demented patients, and may be present very early in the course of the disease. To describe depression observed in patients suffering from dementia. Medline and Google Scholar searches were conducted for relevant articles, chapters, and books published before 2014. Search terms used included depression, dementia, behavioral and psychological symptoms of dementia (BPSD), Alzheimer's disease, dementia with Lewy bodies frontotemporal dementia, Huntington's disease, Parkinson's disease with dementia, vascular dementia. Publications found through this indexed search were reviewed for further relevant references. Depression and dementia are common in older people and their association is very complex. The reported prevalence of comorbid depression or depressive symptoms in individuals with dementia has been quite variable, likely due to differences in methods of assessment, diagnostic criteria, stages of dementia, and other factors. Little empirical evidence is available to guide the clinicians in the selection of treatment. Comorbid depression complicates diagnosis, affects treatment approaches and outcomes, and decreases the quality of life of affected individuals as well as their caregivers. The coexistence of depression and dementia has emerged as a significant public health problem leading to increased health care utilization and costs.