A kitchen next to a hospital clinic in Wales was "unfit for human habitation", BBC Wales has learned.
The premises at Glangwili Hospital in Carmarthen were deemed "severely infested", with hundreds of cockroaches destroyed.
Hywel Dda health board said the kitchen was not used to prepare food for patients.
An investigation by BBC Radio Wales' Good Evening Wales programme found issues at other health board sites.
At two other Hywel Dda hospital sites, a rodent was found in a cleaning cupboard at Bryntirion Hospital, Llanelli, and a dead mouse in a sluice room at Llandovery Hospital.
Shadow Health Minister
Responding to the findings revealed after a Freedom of Information (FOI) request, a spokesperson for the Hywel Dda board said: "The health board takes pest control very seriously and has a contract in place to deal with the presence or evidence of pests swiftly.
"We wish to reassure the public that the area affected is not used to prepare food for patients. It is also separate from the main hospital building."
Other health boards in Wales have revealed details of their pest control spending.
At the Cardiff and Vale University Health Board, it has emerged that pest control services were called 155 times since 2010 to deal with rodent problems, including more than 50 call-outs to the University Hospital of Wales.
The cost to the board over the last three years in dealing with pests, including pigeons, has been £46,000.
A spokesman for Cardiff and Vale said many of their sites back onto parkland or have open fields nearby, and that the pest issues do not mean the buildings are unclean.
Abertawe Bro Morgannwg, which covers Swansea, Neath Port Talbot and Bridgend, has also had to dig deep to cover pest control costs.
Since 2010 until August this year, the board spent £34,000 on pest issues.
That included 21 call-outs to the Princess of Wales Hospital in Bridgend, and the same number to nearby Glanrhyd Hospital.
A spokesperson for the board said the spending included preventative measures.
"Hospitals, by their nature, are buildings with a number of doors and entrances, and they can be sited in areas which back onto fields, hedgerows, shrubbery, etc, which will contain insects or other wildlife," said the board spokesperson.
The cost to Aneurin Bevan Health Board covering the Gwent and Monmouthshire areas of south east Wales has reduced significantly since 2010-11, when it spent more than £28,000 in one year. In 2012-13, that fell to £7,770 - including preventative measures and maintenance.
Since May 2012, Powys Teaching Health Board has called pest control services to hospitals 94 times, at a cost of nearly £6,000.
A spokesman for the board said the majority of the incidents were for garden ants and wasp nests, which the board described as "minor issues" which required management for the benefit of patients and staff.
Cwm Taf Health Board in the south Wales valleys said it would take too many resources to obtain the information requested by BBC Wales, but did confirm it had experienced issues with ants, rodents, insects and birds. It has made 72 callouts over the past year.
Betsi Cadwaladr University Health Board in north Wales said it does not routinely collect this data.
The Welsh Conservatives have described the figures as "astonishing".
Calling in pest control means they know about the problem and are doing something about it”
Dr Hugh PenningtonUniversity of Aberdeen
Darren Millar, the shadow health minister, said: "When you're closing kitchens on the basis that they are not fit for human habitation, you have to ask the question what members of staff were doing and what the culture was like in that kitchen prior to its closure.
"You're never going to completely eliminate pest control problems on the Welsh NHS estate, but I am surprised at the scale of them, and the severity of them."
Dr Hugh Pennington, emeritus professor of bacteriology at the University of Aberdeen, said the issues at Canolfan Gwili at Carmarthen's Glangwili hospital indicated management problems.
"The people running the kitchen obviously have not been up to the job," he said.
"Maybe they haven't been trained or managed properly. It shouldn't happen, particularly in hospitals.
"But there's good and bad news here. Calling in pest control means they know about the problem and are doing something about it.
"But it might be bad in the sense that they might have a problem which has been allowed to fester too long."