Addiction disorders in older age have long been neglected by medicine. Despite continuous progress, significant gaps in knowledge, prejudices, and inadequate care offerings still exist. This work presents the current findings on the topic of addiction in older adults and bridges the gap between addiction medicine and geriatric medicine or gerontopsychiatry. In addition to classic substance abuse involving alcohol, sleep aids, and tranquilizers, it also addresses nicotine, painkillers, and illegal drugs. The foundations, diagnostics, clinical aspects, and therapy are presented in a concrete, practice-oriented manner. Aspects of mental and physical development in the aging process that are particularly relevant to addiction disorders in older adults are comprehensively covered. A focus is placed on the connections between substance use and cognitive impairments or dementia.