In the paper, a simple theory of quantum inteference in a loop structure caused by spin coherent transport and the Larmor precession of the electron spin is presented. A "spin ballistic" regime is supposed to occur, when the phase relaxation length for the spin part of the wavefunction (Lɸ(s)) is much greater than the phase relaxation length for the "orbital part" (Lɸ(e)). In the presence of an additional magnetic field, the spin part of the electron wavefunction acquires a phase shift due to additional spin precession around that field. If the structure length L is chosen to be Lɸ(s)) > Lɸ(e)) it is possible to "wash out" the quantum interference related to the phase coherence of the "orbital part" of the wavefunction, retaining at the same time that related to the phase coherence of the spin part and, hence, to reveal corresponding conductance oscillations. Different mechanisms of spin relaxation, such as Elliot - Yafet, the scattering by the edges and surface the structure and the precession ones, as well as their influence on the spin coherent transport are considered. The quantum interference in time-dependent magnetic field, quantum beats in mesoscopic loop structure, are also discussed. The similarities between this effect and Josephson, scalar Aharonov - Bohm and Aharonov - Casher effects, as well as their differences are treated and possible application of the effect to the construction of the device, complementary to superconducting quantum interference device is analyzed. [ABSTRACT FROM AUTHOR]