We investigated the radiation exposure caused by DIPS, which is used to identify accurate repositioning and tumor location in pediatric cancer patients proton therapy. To compare and analyze DIPS condition, 50 pediatric cancer patients who underwent proton therapy were selected in Ilsan K cancer-specialized hospital from March 2007 to October 2009. For DIP exposure, 0.09~1.57 mGy is measured in AP and lateral directions and 23.55 mGy is measured in CSI patients. In whole brain patient, the amount of a day DIP exposure dose was 1.13 mGy. During treatment period, who exposed the biggest DIP dose are whole brain patients, 632.71 mGy is exposed. It is 1.13% of prescribed dose, represented dose is adequate because it is not exceeded 2% of recommended dose. Even though the exposed dose is not exceeded more than 2% of prescribed in DIP exposure, we should recognize the radiation damage and genetic influences to pediatric cancer patients, who is much sensitive to radiation and has longer mean residual life time. Therefore, DIPS guideline for pediatric cancer patients should be indicated to minimize the radiation exposure.