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Purpose/Objective: Radiation carries the risk of inducing complications directly linked to the amount absorbed by tissues. In this initial study, we compare the helical tomotherapy with standard(AP/PA) radiotherapy treatment for pediatric patients with lung metastasis associated with Wilms' tumor and Ewing's sarcoma. We hypothesize that helical tomotherapy will allow for more effective tumoricidal irradiation while minimizing harmful radiation to proximate sensitive structures. Methods/Materials: The full body CT-scans from pediatrics patients were used to compare two radiotherapy techniques. Treatment plans were designed using HiArt- Tomotherapy and Eclipse planning systems for AP/PA traditional external beam radiotherapy with 12Gy/10x to PTV lung. Optimization was pushed for higher avoidance and data extracted for paired t–test analysis. Results: The volume prescription dose (V12) in both plans showed no significant differences. However, doses of the lung and spinal column were more homogenous in the helical tomotherapy than the AP/PA. There was a statistical significance (p<0.05) at V10 for the esophagus, breast buds, heart, l. kidney, spinal column and thyroid but no significance for r. kidney and spinal cord. At V5 there were no significance for r. kidney, l. kidney and esophagus but all other avoidant structures were statistically significant. The long term effects of these dose volumes is presently little studied. Conclusion: Overall, it was observed that the helical tomotherapy is better for treating volumes that minimize dose to normal tissues and supply uniform doses when needed. As treatment techniques are refined, there is an increased need to understand the effects of lower doses on pediatric tissue. Citation Format: Kofi Sarfo-Kantanka, Richard Crilly, Logan Moll. A comparison of helical tomotherapy with standard radiotherapy treatment planning (AP/PA) in patients with Wilms' tumor and Ewing's sarcoma. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A66.