Antonio Dovalí Jaime s/n, Zacatecas 98068, ZAC., México Internet address: VALERI@CANTERA.REDUAZ.MX Amplitudes for boson-boson and fermion-boson interactions are calculated in the second order of perturbation theory in the Lobachevsky space. An essential ingredient of the used model is the Weinberg's 2(2j + 1) component formalism for describing a particle of spin j, recently developed substantially. The boson-boson amplitude is then compared with the two-fermion amplitude obtained by Skachkov long ago on the ground of the hamiltonian formulation of quantum field theory on the mass hyperboloid, p 2 0 − p 2 = M 2 , proposed by Kadyshevsky. The parametrization of the amplitudes by means of the momentum transfer in the Lobachevsky space leads to same spin structures in the expressions of T matrices for the fermion and the boson cases. However, certain differences are found. Possible physical applications are discussed.