The FT-IR spectra of the surface species arising from the adsorption of methanol, formaldehyde and methyl formate on mixed molybdenumstannic oxide with Mo/(Mo + Sn) = 0.1 are discussed. Methanol is adsorbed mainly in the undissociated form due to hydrogen bond on a cation-anion couple with basic character. Methoxy complex is oxidized to a bidendate formate near 473 K. Hydrogen-bonded H2CO, coordinatively bonded H2CO, bidendate formate and polymer species are observed during the adsorption of formaldehyde at pressure 1.5 kPa. Methyl formate is adsorbed in the form of hydrogen-bonded HCOOCH3, HCOOCH3 coordinatively bonded, methoxy complex and bidentate formate. In contrast to MoO3-SnO2 catalyst with molar ratio Mo/(Mo + Sn) = 0.3, formates are more stable up to 473 K. This can be explained by the contribution of Sn ions during their interaction with CH3OH, H2CO and HCOOCH3. (c) 2006 Elsevier B.V. All rights reserved.