A review of the main applications of infrared spectroscopy of adsorbed CO on heterogeneous catalysis is presented. Special attention is given to the factors that can influence the CO interaction with the solid surface and, as a consequence, to the type and position of the infrared absorption bands for each case. Initially, the most common infrared techniques used in this field are numbered and shortly described. Then, the different type of adsorption modes of CO on a metal surface and their infrared activity are discussed. Afterwards, an analysis of the different factors that can influence the infrared spectra of adsorbed CO is divided in three parts: CO adsorption on noble metals, non- noble metals and bimetallic compounds. From this analysis, a proposal to correlate data of surface structure of metal catalysts, obtained by infrared spectroscopy of adsorbed CO, with catalytic activity is presented.