Purpose : The purpose of this study was to investigate the knowledge of families with demented elderly persons towards dementia. Therefore, this study suggests the need of an educational program provided by a specialist. Subjective : Structured questionnaires were distributed to families visiting the Senior Welfare Center and the Day Care Center for the elderly with dementia in Busan, Gyeongnam. The question retrieval method was post. Questionnaires with a total of 100 respondents were analyzed by　the SPSS 12.0 statistical program. The study period was from July 26th to September 11th of 2010. Research : In the level of knowledge for dementia, average 21.20 out of a total of 30 was revealed, and this is the average 70.67 points out of 100. In the meaningful difference of the level of knowledge related characters of population, people who know about the dementia, or think corporate responsibility, had the higher level of knowledge. In difference of the level of knowledge related characters of population, women and the middle-aged had the higher level of knowledge, and married people had the higher level of knowledge. The level of knowledge was revealed high among people who have higher academic careers, the jobs in management, or professional work as well as sales service. People whose incomes was middle class had the higher level of knowledge for dementia. In the case of people who acquired information by a specialist or care for demented elderly person, the level was high. Conclusion : Based on the results of this of study, we identified that systematic education by a professional will improve knowledge of families with demented elderly persons.