It took an ambulance more than an hour to reach 26 'Delta' calls in Cavan and Monaghan last year.
'Delta'-class calls deal with patients suffering from non-cardiac but life-threatening emergencies.
Figures released to Northern Sound News show this represents less than one per cent of the overall total.
This data released under the Freedom of Information Act shows in one case in Monaghan a person had to wait almost two hours and seven minutes for an ambulance last year.
The HSE says this was due to the first ambulance dispatched being diverted to a more urgent call.
On 25 other occasions it took more than an hour for an ambulance to reach their destination.
15 of the cases were in Cavan, with 11 in Monaghan.
The travel distance involved in cases was blamed in the majority of cases, with the nearest available ambulance dispatched.
The HSE says there were no Echo calls, or those involving cardiac emergencies, in which it took more than an hour for an ambulance to arrive.
Ambulances were dispatched to over 3,500 'Echo' and 'Delta' calls in Cavan and Monaghan last year.
0.74 per cent of those took more than an hour to arrive at the scene.
