Recent demonstration of orbital Hall effect has attracted the community because of both fundamental interest and possibility for efficient control of magnetism. While previous studies focus on the local generation of orbital current by an external electric field, it is important to examine how the nonequilibrium orbital angular momentum flows in mesoscopic solids for comparison of theory and experiment and further development of relevant devices. Unlike spin angular momentum, nonzero orbital angular momentum originates from quantum coherence, so the semiclassical spin diffusion formalism cannot be directly applied to the orbital angular momentum transport. In this presentation, we present how to effectively describe transport of the quantum coherent state and discuss unique features of orbital transport that are absent in spin transport.