Studies of methanol dehydrogenation in the liquid phase with Cu-based solid catalysts have shown (i) the product (methylal) is totally different from that in the gas-solid phase reaction (methyl formate) even using the same catalyst, and (ii) the differences in the calcination atmosphere of the catalyst (N2 versus dry air) have a marked effect on the product selectivity (methylal versus methyl formate). These results are in contrast to the gas-phase reaction (commonly methyl formate). The results arc discussed on the basis of surface species characterized with XPS and XRD.