The present work has investigated the influence of CO on the conventional methanol synthesis from CO2 and H-2 On CU(1 0 0) and the possibilities for hydrogenating CO directly into methanol on modified Cu(1 0 0) single crystals. Adding increased pressures of CO to the reaction proved to be a non-trivial problem due to formation of Ni-carbonyls on the stainless steel parts. The problems encountered using high pressures of CO in such experiments are discussed and solutions for avoiding Ni contamination from Ni-carbonyls are presented. Having this under control, it was shown that the conventional rate of methanol formation from H-2 and CO2 is not influenced at all by the presence of CO. Modifying the Cu(1 0 0) surface by adding Ni and Co strongly changes the reactivity of the surface. Previous work where Ni was used as modifier is reviewed briefly and used to understand the results obtained using Co as a modifier. In none of the cases discussed here was it possible to open a new reaction pathway for hydrogenatings CO directly, although a much deeper understanding of the influence of the chemical potential on the surface composition of alloys was gained.