According to the 2002 census of the National Statistics Institute, Quilleco spans an area of 1,121.8 km² (433 sq mi) and has 10,428 inhabitants (5,378 men and 5,050 women). Of these, 5,486 (52.6%) lived in urban areas and 4,942 (47.4%) in rural areas. Between the 1992 and 2002 censuses, the population fell by 0.6% (64 persons).

The principal economic activity of the area is agriculture with traditional crops such as beets and wheat in addition with vast plantations of exotic radiata pine and eucalyptus. Another important activity is the generation of electric energy with two electric grids at Rucúe and Quilleco, the latter of which was inaugurated 23 July 2007 by former president Michelle Bachelet. It treats and utilizes the flowing waters of the Laja River and its tributaries. Rucúe has a 160 MW installed potential, and its average annual generation is 1.190 GWh. Quilleco has a 70 MW installed potential, and it generates an average annual of 450 GWh.

As a commune, Quilleco is a third-level administrative division of Chile administered by a municipal council, headed by an alcalde who is directly elected every four years. The 2008-2012 alcalde is Rodrigo Tapia Avello (ILE). The municipal council has the following members:

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