The effects of 150 kilogray (kGy) of gamma irradiation on cell-wall constituents of cottonwood (CW), lentils straw (LS), apple pruning products (AP) and olive cake (OC) were investigated. Samples were irradiated by gamma irradiation at a dose level of 150 kGy under identical conditions of temperature and humidity and analyzed for crude fibre (CF), neutral-detergent fibre (NDF), acid detergent fibre (ADF) and acid-detergent lipin (ADL). The results indicate that gamma irradiation decreased CF contents by about 29% for CW, LS and AP and by 17% for OC. NDF values were also decreased by about 4% for CW and OC, and by about 12% for LS and AP. Gamma Irradiation treatment also decreased ADF values only for CW by 8%. ADL contents decreased by 8% for CW and 5% for OC with no effects for LS and AP. The percentage of cellulose (CL):CF ratio increased by 30, 34, 38 and 20% for CW, LS, AP and OC, respectively. Also, the percentage of hemicellulose (HCL):CF increased by 57% for CW and 16% for OC and decreased by 7% for LS and AP. The percentage of HCL:ADL increased by 22% for CW but decreased by 33% for LS and AP with no changes for OC. There were no changes in CL:ADL ratio for all residues.