We have performed diffusion experiments with B-implanted 6H-SiC at temperatures between 1700°C and 2100°C. After diffusion, B concentration profiles were measured by means of secondary ion mass spectrometry. Accurate modeling of B diffusion is achieved on the basis of a kick-out diffusion mechanism which only involves point defects on the Si sublattice. Fitting of our experimental profiles yields data for the B interstitial-controlled B diffusion coefficient which are in good agreement with literature data. Moreover, the analysis of B diffusion provides data for the Si interstitial-controlled B diffusion coefficient which is interrelated with the Si self-interstitial contribution to Si diffusion in SiC. This contribution is found to be two orders of magnitude lower than an extrapolation of Si diffusion data reported in the literature.