The effect of cylindrical solid walls and free surfaces on the orientation distributions of otherwise randomly oriented suspensions of non-Brownian rod-like particles was studied via experimental and computer simulations. Comparison of simulation and experimental results showed that computer simulation is a useful tool in the study of the orientation distribution function of suspensions at relatively high concentrations. The simulation showed good agreement with theoretical predictions for an unbounded suspension of rod-like particles. For systems confined into finite-size cylinderical containers, it was observed that even for extremely small concentrations, the orientation of the rods is not completely isotropic. A linear dependence of the anisotropy in any set container size on the concentration up to the highest concentration examined was determined.