The Welsh Government said they "expect waiting times for diagnostic tests to come down" after NHS statistics showed Wales was the worst-performing country in the UK in that area.
Despite the pressures on the NHS, access to diagnostic tests is improving.
However, the health minister Mark Drakeford acknowledges waits are still too long in some cases, and last month announced £5 million of new funding to help the NHS reduce waiting times for those scans and tests where there are particular challenges.
Speeding up access to these tests will mean that patients get the results faster and can start their full treatment sooner. We expect waiting times for diagnostic tests to come down.
Elin Jones, Plaid Cymru health spokeswoman, said the figures showing that Wales has high waiting list times for life-saving tests highlighted "the stark reality of Labour's mismanagement of the NHS".
The Health Minister needs to take emergency action to bring down these waiting lists and help the thousands of people who are in limbo as they await a diagnosis. We need to make sure that the diagnostic machines are staffed for longer so that they can be used to their capacity.
This will need extra funding, but failure to do so would be condemning patients to wait even longer for basic tests.
Plaid Cymru has long advocated better planning within the NHS so we can plan ahead for the future workforce, keep waiting lists down and make the Welsh NHS the efficient service that it can be.
– Plaid Cymru health spokeswoman and Ceredigion Assembly Member Elin Jones
The Welsh Conservatives have pointed out that waiting time targets from referral to treatment are "consistently" being missed, and that the figures published this morning show 389,019 people - around one in eight in Wales - are waiting for treatment of some kind on the NHS in Wales.
Despite the best efforts of hardworking NHS staff, waiting time targets are being regularly missed and more patients are waiting longer for treatment.
Long waits to start hospital treatment can be distressing and worrying for vulnerable patients and their families.
Waiting time targets are consistently being missed month by month with little prospect of the Labour Health Minister getting to grips with the problem.
Labour’s record-breaking cuts of half a billion pounds to the NHS will only further constrain capacity and make it more difficult for patients to be treated promptly.