Intensity-modulated radiation therapy (IMRT) was put as the development of three-dimensional conformal radiation therapy (3D-CRT). The purpose of the present study is to compare the dosimetric analysis of two techniques of radiotherapy (IMRT) and 3D-CRT, which include target volume and organ at risk for both plans. The present study enrolled that nine patients with different types of brain cancer which previously irradiated from November 2018 to May 2019 were selected in Zhianawa Cancer Center in Sulaymaniyah; all cases were planned again by both techniques 3D-CRT and IMRT. IMRT planning provides reducing the dose of both right and left optic nerve mean dose for right optic nerve 13.70 Gy and left 14.93 Gy compared with the 3D-CRT plan (right optic nerve 23.54 Gy and left 19.13 Gy). P = 0.2 for the right optic nerve and P = 0.56 for the left optic nerve were statistically significant. IMRT plan reduces dose to the optic chiasm compared to 3D-CRT plan, the mean dose of optic chiasm for IMRT was 33.37 Gy relative to 3D-CRT which was 34.28 Gy and P = 0.92. IMRT plan was better than 3D-CRT for many organs at risk, especially for optic chiasm and both optic nerve deliver less dose than 3D-CRT.