Under European law, UK patients who are clinically eligible for NHS treatment can seek it in other EU countries.
They can also reclaim costs of up to what the NHS would have spent.
But fewer than 30 patients in Wales have made such applications during the past three years, BBC Wales has found.
There are concerns that patients and even some medical professionals are not aware of the rules.
Certain procedures require patients to get prior approval from their health board.
The European directive for cross-border treatment came into force in Wales in October 2013 and allows patients to be reimbursed for care in a state-run or private hospital.
It also places a duty on the Welsh government and NHS to provide easily accessible information to patients about their rights.
Anne Botterill, a retired psychologist from Cardiff, faced a wait of over a year for a hip replacement on the NHS after being diagnosed with arthritis last autumn.
"I was in enormous discomfort. I live a very active life... gardening, dancing and walking," she explained.
"I couldn't do any of those things, I stopped them all."
On the advice of her husband David, an academic with an interest in cross-border health-care, she decided to see if her local health board would pay for her surgery at a Belgium hospital.
Mrs Botterill paid Â£9,000 for her surgery and a five-night hospital stay in Ghent and was reimbursed Â£6,500 by Cardiff and Vale Health Board.
Had she chosen to be treated privately in Wales she says she would paid around Â£12,500 and would have been unable to reclaim any of it.
But Freedom of Information requests by BBC Wales show fewer than 30 applications from patients have been funded through this route since 2011.
That included nine patients from Cardiff and Vale Health Board, which reimbursed patients for treatment in the fields of trauma and orthopaedics, dental, urology, spinal trauma and ear, nose and throat surgery at hospitals in Poland, Belgium, Bulgaria, Austria and Slovakia.
In July, 17,649 patients in Wales had waited at least nine months (36 weeks) for hospital treatment -  despite the Welsh government's target stating nobody should wait that long.
The Conservatives's shadow health minister, Darren Millar, said it was clear more needed to be done to highlight the possibility of travelling for treatment.
"Awareness of this EU directive is nowhere near where it should be and that's the fault of Labour ministers alone," he said.
A spokesman for the Welsh government said guidance on the EU directive has been issued to health boards in Wales.
But they made it clear that the EU laws were not a blank cheque for health care in Europe.
"The directive does not allow NHS patients to go anywhere within Europe and get any treatment or medicine they may desire and then seek reimbursement from the NHS," stressed the spokesman.
"For this reason people are strongly encouraged to speak to their health board if they are considering seeking treatment elsewhere."
Patients may be waiting months for NHS operations unaware they could get the health service to pay for quicker treatment in Europe.