Eir has been refused planning permission for three separate applications for masts across Co Cavan, and one in Co Monaghan.
However, the telecommunications provider has received permission for masts in Ballyconnell and Cootehill.
Eir had applied for planning permission to replace existing masts at Eir Exchange sites in Kingscourt and Arvagh with ones that would have been up to 12 meters taller.
However, both applications were refused because it was deemed that the new structures "would have an adverse impact on the visual and residential amenities of the area".
It added that the works would have "set an undesirable precedent for future developments of this nature".
Plans for 18 metre high masts at Eir Exchange sites in Ballyjamesduff, Co Cavan, and Inniskeen, Co Monaghan, were also refused due to the impact it would have visual and residential amenities.
Elsewhere, permission has been granted for works at Eir Exchange sites in Cootehill and Ballyconnell.
Works in Ballyconnell will see an 18 metre high free standing structure replace the existing 16 metre structure on site, while a 21 metre high telecommunications structure will be erected at the Cootehill site.
