New figures show that over 800 patients have been waiting four years or more to be seen by a consultant at a hospital outpatient department, after being referred by their family doctor.
The total number of people waiting for an outpatient appointment, inpatient or day care treatment is now over 218,000, according to the HSE's latest performance report.
Not all hospitals have returned data for this HSE report, so the real figures are likely to be higher.
The hospital responsible for most of the backlog is Waterford Regional, where 570 patients are waiting over four years for orthopaedic care.
Nationally, over 158,000 patients have been waiting since January last year to be seen at an outpatient department.
There are also nearly 60,000 patients waiting for inpatient or day care treatment, of which most are adults.
That puts the total waiting at over 218,000 patients.
The number of people waiting over a year for inpatient or day care is falling.
The HSE report also shows that the executive had exceeded its budget by over €145 million by the end of March.
The Irish Medical Organisation has said there is a critical shortage of consultants in a wide range of specialties that is contributing to long waiting lists.
Professor Sean Tierney, a surgeon and former IMO president, said that in orthopaedics, Ireland has one specialist surgeon for every 54,000 people.
He said that elsewhere in Europe, the number of consultant surgeons in this area was four times higher - one for every 15,000 people.
Prof Tierney said no more hospital beds should be closed until alternative services are in place and essential frontline staff are recruited.