The numerical simulation results on the channeling of ultra-relativistic electrons and positrons with the energy of 270 MeV in a diamond crystal are presented in the paper. Using the pack of applied codes MBN Explorer [1, 2], the trajectories of the charged particles have been determined for the particles’ falling on the 20 μm-length crystal, along (110) crystallographic plane. The channeling parameters and radiation spectra of electrons and positrons were obtained computationally for the cases of the charged particles’ incidence on a straight diamond crystal and a periodically bent one.