Following the 1906 Valparaíso earthquake a local newspaper reported the volcano to have erupted, but a work published in 1917 by Karl Sapper disputed this.

The nearest towns, usually employed as a base for climbers, are Pucón in Chile and Junín de los Andes in Argentina.

There are two paths to the summit: one on the north, starting at 1,200 metres above mean sea level near Tromen Lake and the international Mamuil Malal Pass, accessible via Neuquén's Provincial Route 60; and one on the south, starting beside Huechulafquen Lake, accessible via Provincial Route 61.

Lanín is the easternmost volcano of a north-west south-east oriented chain of three large stratovolcanoes, Villarrica being the westernmost one and Quetrupillán the one in the middle.

Ages of ranging from Late Pliocene to Early Pleistocene have been suggested for the oldest known parts of the volcano, which are dacitic lava flows with columnar joints.