The structure of oxidic and sulfided Mo catalysts supported on activated carbon was studied by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), and extended X-ray absorption fine structure (EXAFS), The activity for mixed alcohol synthesis was also investigated. In oxidic state, the Mo phase on the sample with low Mo loading is mainly present as MoO2, due to the migration of the potassium anions into micropores of activated carbon and the reducing nature of activated carbon at a high preparation temperature. As the Mo loading increases, the interaction between potassium and molybdenum is enhanced. At the MoO3 loading of 72 wt%, Mo mainly exists in the form of K2Mo2O7 species. After sulfidation, the OS substitution takes place; the Mo sulfide phase is highly dispersed as tiny three-dimensional particles at higher loading. Indeed, the results of XRD, LRS, and EXAFS demonstrate that MoS2 is the major phase present after sulfidation, The higher catalytic activity for Mo-K/AC compared to Mo-K/Al2O3 is explained by the difference in the structure of sulfide phase and in the interaction between these phases and the respective supports.