In this study we investigated the mechanochemical hydrogenation of carbon monoxide over nanostructured FeCo- and Mg2Ni-based catalysts. To this aim powdered materials, prepared by mechanical alloying, were subjected to mechanical treatment under CO + H-2 atmosphere. A methodology to evaluate the activity of the solid catalysts on an absolute basis was developed. Conversion data were, indeed, expressed as turnover frequency, TOF, and related to the occurrence of ball to powder collision events through the mechanochemical turnover frequency parameter, MTOF. Differences in the catalytic activity and selectivity were observed for the two FeCo-based studied systems, the solid solution Fe50Co50 and its dispersion on TiO2 support. As for the Mg2Ni system, we explored the possibility to estimate the specific role of hydrogen pre-activation step. The catalytic properties of the mechanically alloyed Mg2Ni system were compared with the conversion data shown by the same system pre-hydrogenated and subsequently milled under CO atmosphere. (C) 2011 Elsevier B. V. All rights reserved.