An overwhelmingly unionist area, Lagan Valley is one of the most prosperous constituencies in Northern Ireland.
The mainly urban constituency contains most of Lisburn District Council and the Dromore area of Banbridge District Council.
Boundary changes mean Lagan Valley lost the Glenavy ward of Lisburn district to South Antrim, and the Dunmurry ward and the northern part of the Derryaghy ward to west Belfast.
In 2007 the DUP won three seats, and the UUP, Alliance and Sinn Féin one each.