It took 2 hours and 26 minutes for an ambulance to arrive at a life-threatening emergency in Co Monaghan.
Volume of work was cited for such a long delay by the HSE.
According to figures released under freedom of information, it has taken over two hours to arrive at 100 emergencies across the country so far this year.
1 hour and 19 minutes was the timeframe for an ambulance to respond to an emergency call in County Cavan.
The figures revealed that in 15 emergency call outs by the ambulance services in Monaghan the wait times all exceeded 1 hour.
While in Cavan emergency calls responded by paramedics took over 1 hour on 10 separate occasions in the period up until the end of May this year.
Under HSE targets, an ambulance should arrive at the scene of a life-threatening heart or respiratory arrest within 19 minutes in 75 per cent of cases.
In all other critical cases, that response time should be met in 45 per cent of cases.
Nationally the longest wait was three hours and 16 minutes in Co Leitrim, with the HSE’s National Ambulance Service blaming the distance for the delay.
The HSE says these figures represent only a fraction of the emergencies dealt with, with 57,240 life-threatening calls in the five-month period across the country.
