The National Parents' Council (NPC) and ISPCC have expressed their concern at the possible hidden dangers for youngsters using websites to send letters to Santa.
The groups have cautioned that those working for sites aimed at very young children may not have properly vetted staff and that some sites are not secure.
At least one site offering children the chance to e-mail their wish list to Santa requests a number of personal details before letters are sent. Those details include the youngsters' name, location, age, sex and e-mail address.
The NPC's chief executive, Ms Fionnuala Kilfeather, said one of the sites was a commercial venture which might take a child's details and e-mail address and "bombard" them with advertisement e-mails offering for sale toys and other products.
The ISPCC's chief executive, Mr Paul Gilligan, said his organisation discouraged the practice of young children giving out any personal or contact information to websites, particularly when the identity of those running the site was not known.
