A high-frequency (95 GHz) pulsed electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) study has been carried out on the shallow boron acceptor in C-13-enriched 4H-SiC and 6H-SiC. From the hyperfine interaction of the unpaired electron spin with the C-13 (I= 1/2) nuclei the spatial distribution of the electronic wave function has been established, and turns out to be highly anisotropic. It is found that there are subtle differences in the degree of localization of this wave function between the different quasi-cubic sites in the polytypes 4H-SiC and 6H-SiC. For the hexagonal site no detailed analysis could be made of the ENDOR data, but the results indicate that here also the spatial distribution is highly anisotropic.