Effects of Ganoderma lucidum (G1) and Krestin (PSK) extracts on spleen, thymus and splenocytes in gamma-irradiated mice were investigated in this study. ICR strain male mice were divided into five groups, Group A was the normal control. Group B, the experimental control, was treated with GI. Group C, the radiation treatment control, was treated with whole body exposure to 4 Gy gamma-irradiation (RT). Group D was treated with RT and G1. Group E was treated with RT and PSK. The dosage of G1 was 400 mg/day/kg body weight and PSK was 500 mg/day/kg body weight. Our results indicated that the relative thymus weight in groups D and E were higher than group C on day 28 after gamma-irradiation. Group D was the highest in all the experimental groups. CD4 and CD8 splenocytes in group D were higher than group C on days 7 and 28, GI was better than PSK in repairing the damage of subset T-cells in the spleen of gamma-irradiated mice.