It was centred on the districts of Ruislip and Northwood in the London Borough of Hillingdon.

This represented the northern half of the earlier Uxbridge constituency which was divided into two following house-building in the area in 1950.

Ruislip-Northwood was a constituency that as such covered slightly elevated and gently hilly outskirts of West London, beginning 12 miles (19 km) WNW of Charing Cross.

1997–2010: The London Borough of Hillingdon wards of Bourne, Cavendish, Deansfield, Eastcote, Harefield, Manor, Northwood, Northwood Hills, Ruislip, and St Martins.

The constituency consisted of the northern part of the London Borough of Hillingdon.