The purpose of this study is to examine the difficulties to talk about the features of developmental disabilities of their own children to the grandparents. The levels of the difficulties were compared in relating to the grandparent's relationships to the mothers by means of a series of questionnaire. As a result, there were some features of developmental disability which was difficult for the mothers to talk to the grandparents, although there were no relation between the frequency of children's contact with the grandparents and the difficulties for the mothers. Also there were not relations between the frequency of explanation to the grandparents about the features of developmental disabilities and the mother's difficulties. Mothers felt more difficult to talk to the parents-in-law and easier to talk to real mother about features of developmental disability. From these results, the necessity of professional facilitation for adequate relationship between mothers and grandparents in assisting effective communication between family members was discussed.