1,500 were in the Regional Hospital Tullamore.
Nearly 3,000 patients were waiting for inpatient or day case appointment at a midlands hospital at the end of May.
New data from the National Treatment Purchase Fund shows 1,500 of those were in Regional Hospital Tullamore, followed by 885 in Mullingar, 409 in Portlaoise.
Almost 350 of the total figure in the region were children.
Nationally, over 87,000 patients are waiting for an appointment, which is 882 more than the figure in April.
As of the end of May, there were more than 705,000 patients in total on hospital waiting lists.