Аннотация:The radiative transport equation (RTE) is now widely known. However, there is only a limited number of problems, which have been solved analytically using it. In this report, in a methodical plan we discuss several basic issues, which can be encountered when formulating RTE for turbid biological tissues. We considered several basic terms and definitions and proposed a way, how one can use them more correctly at the RTE derivation. As an example, we obtained a novel analytical 3D solution for a semi-infinite turbid medium using the single scattering approximation.