More than £50m needs to be spent at Maelor Hospital in Wrexham to prevent patients being put at risk, according to a report.
Members of Betsi University Health Board will consider a report which outlines the "parlous" condition of one of North Wales’ biggest hospitals, which treats 35,000 inpatients and more than 260,000 outpatients a year.
Although there are long-term plans for a major shake-up of health provision in the town, officials say that £50m-£60m must be spent very soon to maintain services in the next 10 years.
The warning comes amid growing concern about the condition of some of the buildings, equipment and utilities on the site.
The total cost of bringing the Wrexham site up to modern standards is put at £284m, compared with £209m for Ysbyty Gwynedd in Bangor and £86m at Ysbyty l Clwyd, Bodelwyddan, where major works have already been carried out.
Work to upgrade high-level risk systems such as ventilation and mains services including water, oxygen and drainage is due to begin.