Scientific studies often exclude institutionalized people. Thus, there is insufficient information about the percentage of older people, who are living in nursing homes. Furthermore, when they move to a care facility, it is questionable whether their new address is officially registered. This is a major prerequisite for their accessibility in studies. By using a standardized questionnaire, the number of nursing home residents in Dortmund was anonymously recorded. Their percentage of the population was determined separately for gender and age. This information was then compared to the official registry. Of those 65 years and older, 5.0% of women and 1.8% of men lived in long-term nursing homes. The percentage of institutionalized people of both genders increases with age; however, the correlation is stronger for women. Overall, 79.5% of the residents are female. To some extent, there were large differences between the information from the care facilities and the official registry concerning the number of residents.