We have examined the effect of the substrate in cubic boron nitride (c-BN) film synthesis by depositing BN films on a variety of materials using ion-assisted pulsed laser deposition. Using optical modeling, we estimated the c-BN content of the films from the measured infrared reflectance spectra. We find less c-BN in films grown on metal substrates than in films grown on Si and SiC/Si substrates. The c-BN content of the films decreased with decreasing substrate microhardness. This result is qualitatively consistent with the model of stress-induced c-BN film formation.