Craniospinal irradiation (CSI) has become an important treatment method for primary tumors. three dimensional conformal radiotherapy (3DCRT) and intensity modulated radiation therapy (IMRT), are used in CSI treatment. A number of patients were selected for this study were diagnosed with medulloblastoma disease. In the 3D technique, two lateral parallel opposed fields were used for the head irradiation and a matched posterior field for spine irradiation. IMRT technique was planned using a seven field inverse treatment planning technique. The beams were distributed around the target with equidistant gantry angles with gantry angles of 0°, 50°, 100°, 150°, 210°, 260°, and 310° were used and the Homogeneity Index (HI) and Conformity Index (CI) is calculated for all targets. There is a good coverage, low maximum doses in the brain with IMRT in comparison to 3D techniques, while the conformity and homogeneity index of the brain dose and spinal dose is nearly the same in IMRT and 3D techniques. IMRT achieves the lowest dose to all organs at risk while the 3D techniques show little difference. It is recommended to use the IMRT technique in the treatment of medullablastoma cases to achieve good coverage for the target (brain and spinal cord) and more sparing to organs at risk.