Miriam O'Callaghan appealed to the nation to dress up in costume and hold a Halloween fundraising party for Temple Street Children's Hospital.
The broadcaster joined with some little hospital patients to launch the Trick or Treat for Temple Street appeal yesterday.
As the 2014 ambassador for the appeal, Miriam is helping the Dublin hospital to encourage families, businesses, pubs and schools to hold a Halloween party and help a sick child.
Sponsored by MiWadi, the nationwide appeal will run throughout October.
The broadcaster said: "Trick or Treat for Temple Street is so simple - have a party and help sick children. We all hold Halloween parties every year, so why not do it for these amazing and brave young children.
"The hospital has a very special place in my heart... let's get this party started!"
The money raised will help fund the building of a new neurology unit.
The doctors and nurses in this unit care for some of the hospital's most vulnerable patients suffering from complex disorders such as epilepsy, cerebral palsy and brain tumours.
Patient numbers are increasing and many of the facilities at the hospital are out of date.
"Many of our sickest kids depend on equipment bought by generous donations to stay alive," said Denise Fitzgerald, chief executive of fundraising.
"This year, we need to raise over €5m to ensure that our patients receive the best care possible. Everyone loves a Halloween party - an excuse to dress up and have some fun in work, in school or with the family. But these Halloween parties can truly mean the difference between life and death. We urge everyone: please help us to help them," she said.