This paper reports on a simultaneous electron diffraction and mass spectrometric study of the saturated vapor of lutetium trichloride at T = 1070(10) K. It is found that the vapor consists of the monomer LuCl₃ [91.6(1.2) mol. %] and dimer Lu₂Cl₆. The following parameters were obtained for LuCl₃ (r_g configuration): r_g(Lu-Cl) = 2.403(5) Å, r_g(CL.Cl) = 4.119(18) Å,_g(Cl-Lu-Cl) = 117.9(1.3)ℴ. Calculation of vibrational corrections for a transition from r_g to r_α geometry gave a planar equilibrium configuration for LuCl₃ with D_3h symmetry, whereas our previous electron diffraction study recommended a pyramidal configuration. Possible reasons for this controversy are discussed. The geometry of the Lu₂Cl₆ molecule of D_2h symmetry is described by the following parameters (ra configuration): r_α(Lu-Cl_t) = 2.366(5) Å, r_α(Lu-Clα) = 2.589(24) Å, ZCl_t-rLu-Cl_t = 119(7)ℴ, ZCl_b-Lu-Cl_b = 84(2)ℴ. The mean energies of the terminal [E(Lu-Cl_t) = 485 kJ/mole] and bridging [E(Lu-Cl_b) = 292 kJ/mole] bonds of Lu₂Cl₂₆ are estimated.