The chapels were built for £5,300 in 1859
Two cemetery chapels feature in an annual list of the ten most endangered Victorian and Edwardian buildings.
The Victorian Society included the grade II-listed twin chapels in Cathays Cemetery, Cardiff, following a public appeal for nominations.
Cardiff Council, which owns the chapels, has earmarked up to £200,000 for roof repairs but full restoration could cost more than £1m.
The chapels, which have a central bell tower, were built in 1859 for £5,300.
Friends of Cathays Cemetery secretary John Farnhill said: "It's good that other societies and organisations take an interest in the cemetery chapels.
"They're a fine example of Victorian architecture in Cardiff that is disappearing with all the redevelopment.
"We're aiming to get a commitment from the council to get them fully refurbished and restored."
The council is providing up to £200,000 for repair work to the chapel roofs to prevent the buildings from deteriorating further before more cash can be found.
Stonebridge School, Brent, London
Gustav Adolfs Kyrka (Swedish church), Liverpool
Newsome Mill, Huddersfield
Red Lion pub, Handsworth, Birmingham
St Marie's Church, Widnes, Cheshire
Cathays Cemetery chapels, Cardiff
Moseley Road Baths, Birmingham
Holy Trinity, Hove, East Sussex
Palace Theatre, Plymouth, Devon
Fletcher Convalescent Home, Cromer, Norfolk
SOURCE: The Victorian Society
Mr Farnhill said it was difficult to put a figure on the cost of full restoration but more than £1m had been suggested.
He said ideas were being considered for the future use of the chapels but the council, as owner, would have the final say.
"The floors are in a state, the walls are in a state and there's no gas or electricity or internal plumbing," said Mr Farnhill.
"There are two chapels and one might be restored as a chapel and double up as a lecture theatre or something like that.
"The other might be an exhibition space and/or interpretation centre for the cemetery as there's wildlife there and there's the history."
A family history resource centre was another idea, but Mr Farnhill stressed they were only suggestions at the moment and nothing had been confirmed.
Director of the Victorian Society Dr Ian Dungavell said: "If repair work doesn't start on these buildings soon, it's hard to see how they will survive.
"That would be a great shame both for local campaigners and for Cardiff council, which acted so positively in awarding these fascinating buildings a grant.
"We know finances are tight for everyone at the moment, but we hope that the money can be found to give these outstanding records of Welsh religious history a new lease of life."
A spokesperson for Cardiff council said: "The council is aware that the chapel at Cathays Cemetery is in need of restoration work.
"This is why an initial total of up to £200,000 is being made available to fund repairs to the chapel roofs in an attempt to save the buildings from any further deterioration and decay until further funding can be identified to fully restore the building.
"It is hoped that some works will be started early in 2009."
The Victorian Society received nominations for this year's top ten from members of the public, heritage enthusiasts and campaigners.
Other buildings on the list for Wales and England included Moseley Road Baths in Birmingham, the Palace Theatre in Plymouth, Devon, and St Marie's Church in Widnes, Cheshire.
Last year's list included the Llanfyllin workhouse in Powys, a building that has also featured in the BBC's Restoration programme.