A new approach is proposed which allows us to calculate molecular conformations of organometallic molecules within the framework of the MM3 force field. The ligand positions in the coordination sphere of the metal atom are mainly determined by minimization of the interligand nonbonded energy. For a description of the metal-ligand interactions (pi-bonding), a very strong but otherwise ordinary (Hill type) van der Waals potential is used. Using this approach, the conformations of the bent sandwich metallocenes MCp(2) (where M are metals of main groups II or IVA or lanthanides II) were reproduced. It was shown that, when the interplanar distance between the planes of the Cp ligands are short, the ligands have a parallel orientation. When the distance is large (when the metal atom has a large radius), the interplanar distances become longer and the ligand planes do not stay parallel, but the molecule "bends" so that these planes intersect. The influence of bulky substituents,on the bending angle was shown. Calculations were also carried out on crystals of these molecules, to determine the effect of crystal packing. The possibilities for the accurate prediction of the conformations;of molecules of this type of structures (not yet investigated experimentally) on the basis of quantum mechanics and molecular mechanics are discussed.