The interaction between HCOOH and TiO2-supported Pt catalysts was investigated at 300-473 K. The formation of surface species was studied by FTIR and the simultaneous monitoring of the gas phase revealed the formation of the products during the interaction. Besides the dissociative adsorption of HCOOH and the derivatives of this process, the formation of formaldehyde both in the adsorbed layer and in the gas phase was observed. The amount of formaldehyde depended on the pretreatment and on the metal content of the catalysts as well as on the temperature of the interaction. The formaldehyde formation might be an independent reaction pathway in the catalytic transformation of HCOOH. (C) 2004 Elsevier Inc. All rights reserved.