Three different silica-supported nickel samples were prepared by successive adsorption, reduction, and passivation (SARP) of nickel. The materials obtained were characterized by various techniques (TEM, XRD, H2 chemisorption, FTIR spectroscopy of adsorbed CO, FMR). Metal nickel particles were uniformly distributed by size with all samples. With increasing the number SARP cycles (1, 3, and 5, respectively) the metal concentration (3.6, 7.6, and 12.6 wt%, respectively) and the mean particle size (4–5, ca. 6 and ca. 7 nm, respectively) also increased without substantial increase of the number of metal particles. The samples were tested as catalysts in methanol decomposition to CO and H2. It was found that this reaction was structure sensitive and the turn-over frequency decreased with the particle size increase. In contrast, the secondary interaction between the reaction products, i.e., CO methanation (occurring above 515 K) appears to be structure insensitive.