Sligo Regional Hospital could become nothing more than an add-on within a larger group.
That's because of fears that Sligo and Letterkenny General Hospitals will join the already established Galway and Roscommon group of hospitals.
And Mayo may be added to that.
IMPACT official Richy Carrothers said: "If this comes to pass, the two North West Hospitals will simply be add-ons to the structure that is already in place.
"The Galway and Roscommon Group have their own senior management structure, clinical structure and Board.
"We are concerned that the North West is simply being added for the purpose of convenience rather than making strategic sense".
He made his comments in the aftermath of an IMPACT briefing in the Dail for Sligo and Donegal Oireachtas members.
The union has expressed its concerns ahead of the much awaited "Higgins Report."
It is named after Professor John Higgins, Chair of the Hospital Group Strategic Board.
That Report is expected to be published soon.
Mr Carrothers said: "It is of concern that our two hospitals in the North West are being forced into a very large structure that may not be fit for purpose.
"Equally so, clinical decisions and priorities are likely to be made in Galway rather than at local level.
"Galway will to be the tertiary centre for care and possibly at the cost of Sligo and Letterkenny.
"It may result in the two North West hospitals having to compete against each other.
The Department of Health said the Report on hospital groups seeks to ensure the provision of an optimum configuration for hospitals in the region to deliver high quality, safe patient care.
It seeks to do this in a cost effective manner and to maximise the range of services available to the population.
The Department added: "Proposals to combine hospitals of varying model, size and relative strength is not without risk and there is a reasonable concern that services could gravitate towards the centre.
"The report is explicit in its recommendations to ameliorate that risk. Once set up, a key requirement is that each group must prepare a strategic plan in line with the report's recommendations.
"It is intended that the operation of the groups will be rigorously reviewed against the report's recommendations.
"This is aimed at ensuring that all hospitals in each group do not compete but work together as a single cohesive entity."