The mechanism for reaction of CH3O with NO2 is investigated at DFT (B3LYP), MP2 and QCISD levels with 6-311 ++G(d,p) basis set. The geometries and vibrational frequencies of stationary points on potential energy surface are obtained. There are six possible reaction paths that involve 8 conformers, 13 transition structures and 4 possible products for the title reaction. The recombination channel for the product CH3ONO2 is dominant. At the adopted levels of theory, the disproportionation channel, which is thought to be possible by simple intermolecular H-atom abstraction conjectured experimentally, has not been found. (c) 2005 Elsevier B.V. All rights reserved.