Some politicians in north and mid Wales believe that sending patients to England for specialist treatment is being increasingly discouraged.
Patients have been treated at centres of excellence in England
Figures indicate that in the past three years there were over 53,000 hospital treatments involving patients from Wales at hospitals over the border.
Health Minister Edwina Hart said the aim was to provide services as close to patients as possible.
But she said there would always be cases where patients had to travel.
Politicians are asking if there is a deliberate attempt to create a new demarcation between Wales and England.
Wrexham Labour MP Ian Lucas argued strongly that his constituents should not be disadvantaged because of devolution.
He said specialist medical services were expensive and that he has no problem with people from north Wales travelling to England if they can access treatment there.
NHS trusts in England have the flexibility to charge per case, but Mr Lucas believes policy-makers in Wales should be able "to work out practical long-term arrangements with trusts in England"
He argued that the cross-border health issue demolished the Conservative argument that Welsh and Scottish MPs should have no voice in Parliament on the development of policy in England.
In the past three years over 30,000 treatments were carried out at the Countess of Chester Hospital on patients from Wales, while the NHS Children's Trust in Liverpool conducted 6,000.
They are both specialist centres and highly regarded as centres of excellence in their respective fields.
Doctors are being discouraged from sending patients to Gobowen
The question is whether Wales in general, and north Wales in particular, has sufficient numbers to justify developing its own specialist services.
People are up in arms because of their belief that there are plans by Mrs Hart to insist that patients from the region needing specialist neurosurgery will have to travel to Cardiff or Swansea,
A recent protest in Colwyn Bay illustrated clearly that the minister had yet to convince her critics that her policy meant that people would be discouraged from going to the specialist neurosurgery unit on Merseyside
Clwyd West Conservative MP David Jones, who organised that protest, said he accepted the concept of a Welsh NHS but that ministers were being over-dogmatic.
An "all-Wales solution" to medical problems should not work to the detriment of patients in north Wales, Mr Jones said.
The Gobowen Orthopaedic hospital in Shropshire has treated generations of patients from north Wales, but that too is changing
Cart before horse
Dr Phil White from the British Medical Association said clinicians are currently being discouraged from sending patients to the hospital in Shropshire because of the cost.
But he said there must be negotiations between the assembly government and the local Health Trust in Gobowen to find a way through the problem.
Patients from Mid Wales who need specialist medical treatment often have to travel to Shrewsbury.
Brecon and Radnorshire AM Kirsty Williams, former chair of the assembly health committee, said there was a real fear that the assembly government was trying to put the cart before the horse.
What seems sensible to a politician sitting behind a desk in Cardiff, said Ms Williams, was not always the most sensible strategy.
She said money had to be spent on services where people wanted them.
In a statement, Mrs Hart said the aim was to "provide as many services as close to the patient as possible where they can be delivered safely and sustainably".
"However, when it comes to complex treatments patients may have to travel further to specialist regional centres so that they receive the most appropriate care, whether that be in Wales or England," she said.
She said there would "always be instances where patients will have to travel to England for highly specialised treatment that may only be on offer at a few centres in the UK.
"The key point is that patients have access to the most appropriate treatment when they need it wherever that may be."
Mrs Hart also stressed that no changes had been made to arrangements for neurosurgery patients, and she had asked a distinguished surgeon, James Steers, to lead a review.