The structural parameters of the (I-2 (+) pound//C-av )-YbF, ((1)A(1)//C-2v )-YbF2, ((2)A (2) (') //D-3h )-YbF3, (Ag-1//D-2h )-YbF2Yb, (Ag-1//C-2h )-FYbF2YbF, ((1)A(1)//C-2v )-FYbF2YbF, ((1)A(1)//C-2v )-YbF2YbF2, (B-3(3u) //D-2h )-F2YbF2YbF2, ((2)A'//C (s) )-FYbF2YbF2, and (B-3(2)//D-2v )-F2YbF2CeF2 molecules have been determined. Disproportionation of ytterbium monofluoride (2YbF -> YbF2 + Yb + 0.46 eV) is less exothermic than dimerization (2YbF -> YbF2Yb + 2.10 eV). The bond energy of the ytterbium difluoride molecules in the trans dimer (2.93 eV) exceeds those in the cis dimer (2.86 eV) and the coaxial dimer (1.66 eV). Ytterbium trifluoride dimerizes exothermically (2.95 eV) without spin pairing. The dipole and quadrupole moments of the molecules as well as the charges and spin populations of the atoms and the valence electron configurations of the lanthanides have been calculated.