Beta and neutron attenuations of poly(imide siloxane) block copolymers were compared to evaluate radiation penetrations into flexible sheet (BI) and pellet form BII grains. The modification of BII polymer has improved its radiation shielding properties of poly(imide siloxane) block copolymer as the result of the pelletization. The linear attenuation coefficient of BII sample was determined as similar to 0.073 (1/cm) and the half value layer was at similar to 9.5 cm for negative beta particles. Besides, the total macroscopic cross section was at 0.047 (1/cm) and the half value layer of BII sample was determined at 14.74 cm for neutrons. The variations of beta and neutron attenuations indicated the structural changes in the poly(imide siloxane) block copolymer depended on the critical production parameters at the production step. The pelletization of the grains of BII improved beta and neutron shielding properties of poly(imide siloxane) block copolymers for the use in medical applications.