The quasipotential approach in quantum field theory is used to derive relativistic threshold resummation factors in quantum chromo­dynamics.

Low energy interactions of scalar mesons are investigated in the Quark Confinement Model. The good description of these decays in two-quark scheme was achieved by means of the addition term in the scalar-quarks Lagrangian.

A relativistic inverse problem is solved for the case when the total quasipotential simulating the interaction of two relativistic spinless particles of unequal masses is the superposition of a local quasipoten­tial and a sum of nonlocal separable quasipotentials. The problem is investigated within the relativistic quasipotential approach to quan­tum field theory. The local component of total interaction is supposed to be known and it not admits bound states. It is shown that the non­local separable components of total interaction may be reconstructed if its the local component, the phase-shift additions and the true bound state energy are known.