RTÉ News has learned that Dublin's Tallaght Hospital has a backlog of around 6,000 reports on X-rays and other scans, which have yet to be provided to doctors who referred patients for checks.
The problem relates to delays in typed radiology reports.
These include X-rays, CT, MRI and ultrasound scans, which have been read by a specialist and the results dictated onto tapes for a report to be typed by clerical staff and issued to the referring consultant.
The problem relates to adult patients only.
Tallaght Hospital Chief Executive Eilish Hardiman told RTÉ News that there is no risk to patient safety.
She said that the current tape recordings were five weeks old and when the standard turnaround time is taken into account, the current delay in typing reports is two to three weeks.
Ms Hardiman said all urgent reports are typed within 24 hours.
An internal memo circulated in the hospital's radiology department, seen by RTÉ News, warns that because of the backlog, patients may be at continued medical risk from lack of transmission of findings to their referring doctor.
It says the problem has been highlighted to senior hospital management for the past four months but attempts to tackle the backlog have not succeeded.
The hospital says that any critical findings spotted on a scan will not be put onto the backlog but will be immediately brought to the attention of the referring doctor.
It plans to introduce an interim solution from 8 April, which will deal with around 65% of scans, using a voice recognition system attached to its existing PACS (Picture Archiving and Communication System) in operation since 1998.
During the first quarter of next year, it expects to roll out the full national integrated medical imaging system (NIMIS), which many hospitals already have.
Tallaght Hospital says that extra clerical support has been moved to the radiology department, but the hospital must operate within its budget and cannot use agency staff or recruit more staff.
In 2009, Tallaght Hospital was at the centre of a major controversy after it emerged that there was a backlog of over 57,000 unread X-rays and also unprocessed GP referral letters.
That controversy led to an independent inquiry which pointed to problems in radiology, IT and in tackling the backlog.
In 2011, it also emerged that the hospital had outsourced the typing of medical reports and letters to a private firm in the Philippines.