When parents as primary care takers to the mentally disabled adult are no longer taking care of their care-needed offsprings because of their own death or illness, instead themselves. who take care of their offsprings with the mental disability? Therefore, 'permanency planning' is very important for reduction of parents' care burden and social integration of mentally disabled adults. Accordingly, this study aims to find out factors which are related to permanency planning for adults with the mentally disability For the purpose of the study, 192 parents of the adult with the mental illness and mental retardation were conducted a survey regarding type of permanency planning, and its related factors including social functioning level of the mentally disabled, care burden, parents' self-perception of being aged, help from offspring without mental disability, social support, and financial ability. Furthermore, this study examined correlation between these factors and residential planning. Results obtained by the study were as follows: 1) 51% of the parents are having a plan for institution and most parents want other family member to take care for financial planning for their mentally disabled offsprings. 2) As a result of multiple regression for finding out factors which affect parents' permanency planning, social functioning level of the mentally disabled, parents' self-perception of being aged, help from offspring without mental disability, social support, and financial ability were statistically significant influenced factors, which has 23.3% of explanatory power. 3) As a result of step-wise multiple regression, financial ability, parents' self-perception of being aged, and help from offspring without mental disability were the most powerful influenced factors for permanency planning. 4) In case of having a plan for residential types-which are institution and community living-, parents who have a plan for the mentally disabled offsprings' future residence as community living than institution have the offsprings with more social functioning and also have more help from offspring without mental disability. Therefore, this study concluded that welfare policy for mental health and the handicapped which secure various types of community living facilities and income security is strongly needed. At the same time, mental health profession is needed to have more active interest and intervention for permanency planning for their adult clients and parents.