More than half of grandparents in a new national survey were concerned that their grandchildren might become involved in drugs.
Asked about their concerns for themselves and their grandchildren, 22 per cent expressed worries about alcohol, 10 per cent about sexual promiscuity and 52 per cent mentioned drugs, according to the findings in "Grandparenthood in Modern Ireland".
Some grandparents thought their grandchildren were becoming dominant in the household. "They attributed this shift in the balance of power to both parents working and the guilt they might feel because their children are cared for by childminders or are in creches," the study says.
"Additionally, grandparents reported that when working parents arrive home in the evening they are too tired to interact with their children, feel guilty and compensate by acquiescing to their demands.
"These two factors, according to some grandparents, lead to a shift in power from parent to child in these families. Only time will tell if this phenomenon is on the increase. If so, its implications for Irish society and family life may be a cause for concern, but, as yet, unknown."
A good education for their grandchildren was the social policy given priority by most grandparents. They said there should be some recognition of the value of grandparents, their importance within the family structure and their contribution to society.
More than a quarter of grandparents in the survey said they were loath to interfere in their children's lives, even if they considered their parenting style contrary to their own.
The study says this finding, especially in relation to child rearing and discipline, was remarkable. "It may indicate a shift in the balance of power in the extended family," the report states.
"Did grandparents of yesteryear interfere and wield the power over their extended family? The perception among some grandparents is that they did."
Fifty-eight grandparents - 44 women and 14 men - were interviewed for the research, the first into grandparenthood in Ireland.
They were aged from 40 to 92, half were widowed, while almost a third had a disability.
On average, they had 10 grandchildren and saw them at least once a week.
Nine grandparents believed their grandchildren had too many toys and games, and were fearful that their imaginations were being stunted because they had forgotten how to play.
The Minister for Social, Community and Family Affairs, Mr Ahern, whose Department funded the study, said the role of grandparents was under-recognised and the resources they could offer to their families and communities should be more widely used.
He said: "The development of future family policy to the benefit of society as a whole can only be helped by such research."