Each constituency elects one Assembly Member by the first past the post electoral system, and the region as a whole elects four additional or top-up Assembly Members, to create a degree of proportional representation. The additional member seats are allocated from closed lists by the d'Hondt method, with constituency results being taken into account in the allocation.
As created in 1999, the region covers the most of the preserved county of Clwyd, part of the preserved county of Gwynedd, and part of the preserved county of Powys. Other parts of these preserved counties are within the Mid and West Wales electoral region. For the 2007 Welsh Assembly election, however, boundaries will change, and the region will cover all of the preserved county of Clwyd and part of the preserved county of Gwynedd. The rest of Gwynedd will be in the Mid and West Wales region.