Extending from Youghal in the east of the county to the borders of Kerry in the west, the city of Cork was included in this brigade area.  Its southern limit was at Ballinhassig and its northern boundary at Donoughmore.
There were two battalions in the city (north and south of the river Lee) and others were centered at Cobh, Donoughmore, Macroom, Ballinhassig, Ballincollig, Carrignavar, Ballyvourney, Passage West and Youghal.

 Covered an area extending from Ballynoe, north of Midleton, to the Kerry border west of Millstreet and Newmarket. It was bordered on the south by the Mushera mountains and on the north by the Limerick county boundary.
Batallions were located at Fermoy, Castletownroche, Mitchelstown, Charleville, Mallow, Kanturk, Newmarket and Millstreet.

* In May 1921, a fourth Brigade was formed by dividing Cork No. 2 Brigade area. The 4th. Brigade area encompassed the north-west of the county and took in the towns of Charleville, Mallow, Kanturk, Newmarket and Millstreet among others.

Extended from Ballinhassig (15 miles from Cork city) towards the Kerry border in the west and reaching the Atlantic seaboard in the south/south-west.
Batallions were centered at Bandon, Clonakilty, Dunmanway, Skibbereen, Bantry and Castletownbere.