The decision to build a co-located private hospital on the site of Tallaght Hospital is expected to provide up to 200 extra hospital beds.
The Board of Tallaght Hospital has decided that the project should go to tender, despite concerns about the bed mix of private and public patients in the hospital.
The Adelaide Hospital Society had raised concerns about the plans but now says the same doctors will work in both the private and public hospital.
A society spokesperson says today's decision is the only way to meet the need for extra beds at Tallaght Hospital.