Children's Hospital development board member, businesswoman Norah Casey, has repeated the Mater Hospital site as the best location for the new facility.
Speaking at the INMO conference in Killarney, Ms Casey said she would be concerned about choosing another site because it might delay the project further.
There are a number of other sites in contention, including St James Hospital and Tallaght and Connolly hospitals.
Speaking at the INMO conference in Killarney Ms Casey said her preferred location had always been the Mater site.
An Bord Pleanala rejected planning permission for the Mater site because of the impact it would have on the Dublin skyline.
However, a revised application has been submitted. A decision on that application is due at the end of the month.
Norah Casey said the board examined the Mater site in full and it remained her preferred choice.
"I'm worried about the constant delays. I think that if we move to another site, it will take at least another year...We've been given the old Mater site, which means the building can drop a number of floors and maybe assuage some of the concerns that An Bord Pleanala had."