  It is shown that under certain conditions the resonant transport in
mesoscopic systems can be described by modified (quantum) rate equations, which
resemble the optical Bloch equations with some additional terms. Detailed
microscopic derivation from the many-body Schr\"odinger equation is presented.
Special attention is paid to the Coulomb blockade and quantum coherence effects
in coupled quantum dot systems. The distinction between classical and quantum
descriptions of resonant transport is clearly manifested in the modified rate
equations.
