Measurements of both through-thickness and lateral thermal diffusivities are described for a SiC/SiC ceramic matrix composite material. The measurement approach is one-sided and is based on the time-resolved IR radiometry method in which the specimen is illuminated with a step heating pulse and the resulting temperature rise is monitored with an IR focal plane array. An area heating source is used for the through-thickness measurement of thermal diffusivity and a line source is used for the lateral thermal diffusivity measurement. The result indicate that the thermal diffusivity values obtained using a model assuming surface absorption and emission have to be corrected since the composites show some IR transparency accompanied by strong scattering. Additional measurements are presented on CMC components structures with possible porosity at bonds.