The computational modeling of ring-chain equilibria for the ring-opening cross-metathesis of cyclohexene (CH) with 1,2-dicarbomethoxy-ethylene (DCE), 1,4-dicarbomethoxy-but-2-ene (DCB) and ethylene at T = 298.15 K using the B3LYP/6-31G(d,p) level of theory revealed that CH and ring-opened products equilibrium is shifted towards the thermodynamically stable six-membered ring. The calculations demonstrated that carbonyl-containing olefins can completely drive the equilibrium in the cross-metathesis with cis.cis-cycloocta-1,5-diene (COD) towards the ring-opened products. (C) 2005 Elsevier Ltd. All rights reserved.