In small particles of chemical vapor deposited (CVD) diamond and polycrystalline thin films composed of the particles, the recombination radiation of free excitons and bound excitons associated with multiple phonons has been observed using cathodoluminescence. The bound excitons are due to neutral acceptors of boron in the diamonds. The cathodoluminescence imaging reveals that the recombinations of free excitons are located at {100} sectors. The crystal perfection and purity is high in {100} sectors compared with {111} sectors formed in the CVD process.