[2] The Urban District of Runcorn was transferred from Northwich and Lymm was previously part of the abolished constituency of Bucklow.

The Rural District of Runcorn (including Frodsham, Helsby, Grappenhall and Stockton Heath) was previously split between Knutsford, Northwich and the abolished Eddisbury constituency.

From local government boundary changes on 1 April 1974 until the constituency was abolished at the next parliamentary boundary review which came into effect for the 1983 general election, the constituency comprised parts of the expanded Borough of Warrington and the newly formed Borough of Halton, and the District of Vale Royal, but its boundaries were unchanged.

On abolition, the western half of Runcorn was included in the new constituency of Halton along with the town of Widnes (on the northern side of the River Mersey).

The eastern half of the town formed part of the Weaver Vale constituency, along with Northwich, Frodsham, Helsby and surrounding areas.