Fears over hospital's future after report leak.
Hywel Dda Health Board is planning a pounds 38m upgrade to Bronglais Hospital, in Aberystwyth.
Campaigners have claimed services are being shifted from mid Wales' only district general hospital after a leaked report said it was to be downgraded.
Former Ceredigion MP Lord Elystan-Morgan chaired the meeting on Friday.
He said: "On the one hand you have a massive capital expenditure, pounds 38m - it's a lot of money.
"On the other hand, what it does is make up for the lack of investment that has occurred over the years.
"Theatres now are obsolescent to the point that they can no longer deliver their services in safety and, of course, this money now is being paid as compensation for that.
"But at the same time, the process of running down the number of beds continues."
The health board said the leaked report was out of date.
Hywel Dda Health Board chairman Chris Martin said in a letter: "This major investment is the biggest capital project in the Hywel Dda Health Board area and should put an end to suggestions of disinvestment, loss of services or the hospital being under threat.
"The future of Bronglais General Hospital is secure and the health board is committed to ongoing investment into hospital."