It has taken an ambulance at least an hour to arrive at a life-threatening emergency more than 120 times this year.
On one occasion, it was nearly four hours before a patient was attended to.
According to guidelines from the Health Information and Quality Authority (HIQA), an ambulance should arrive at life-threatening emergencies in less than 19 minutes in 80% of cases.
However new figures - released to Newstalk under the Freedom of Information Act - show this target isn't being met in many areas in the country.
On 123 occasions in the first nine months of this year, it was more than an hour before an ambulance arrived.
Nine times this year, it took at least an hour for an ambulance to arrive at a life-threatening emergency in Mayo - one of which was 3 hours and 50 minutes.
Stephen McMahon from the Irish Patients Association said the figures are a cause for concern.
He observed: "We would hope that the National Ambulance Service would be reviewing each and every case that's outside the safety of 90 minutes."
Of the response times of more than an hour, 26 were in Wexford, followed by 20 in Cork and 13 in Kerry.
Speaking as an independent Councillor, paramedic Ger Carthy said it's a big worry for the area's growing population.
He explained: "Wexford is predominantly a tourist destination for four months in the summertime, and our population increases by approximately 50,000 people.
"Unfortunately, the National Ambulance Service can't be at every corner to respond to those calls... it is somewhat concerning."