The work is concerned with structure effects exerted by molecules of substituted acetylenes and ethylenes (cyclopropyl, cyclopentyl, cyclohexyl, phenyl) in heterogeneously catalyzed hydrogenation on platinum and palladium supported catalysts. Kinetic parameters, acquired from hydrogenation of individual model substances as well as binary systems in competitive arrangements enabled discussion of structural effects in heterogeneously catalysed hydrogenation. The method of competitive hydrogenation allowed the assessment of the relation between the molecular structure and the rate of a surface reaction in parallel with the stability of the surface complex. (C) 2003 Published by Elsevier B.V.