Layered mesostructured manganese oxide (mesostructured MnO2) was synthesized using manganese chloride and lithium hydroxide as the raw materials and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Poly(aniline-co-o-anisidine)-intercalated mesostructured MnO2 composites (P(An-co-oAs)/MnO2) were synthesized in an organic solvent through the exchange reaction between the CTAB in MnO2 gallery and the P(An-co-oAs). The interlayer spacing (I-c values) of mesostructured MnO2 enlarged from 2.52 to 4.41 nm as the added amount of P(An-co-oAs) increased from 0 to 0.5 g per 0.5 g of mesostructured MnO2. The regularity of the layered structure of the composites was firstly decreased due to intercalation of low amounts of P(An-co-oAs). However, with increasing the intercalated amount of P(An-co-oAs) the layered structure of the composites becomes more regular. The electrical conductivity of the composites is 10(2) to 10(3) times higher than that of the mesostructured MnO2. (c) 2007 Elsevier Ltd. All rights reserved.