The aim of this study was to evaluate the incidental doseof the liverreceived in breast cancer radiotherapy and to investigate the effects of intensity modulated radiation therapy (IMRT) on liver doses.The breast treatment plans of 225 women withright–sided breast cancer who underwent postoperative radiotherapy were retrospectively examined.Liver V20 (cc) and liver V10 (cc) with IMRT were significantly higher in both with boost and no boost groups.Liver Dmean, V20 (%) and V10 (%) with IMRT were statistically higher in both with boost and no boost groups in which the whole liver was displayed.Liver may be affected at different rates due to anatomic variations in breast cancer radiotherapy. In right–side breast cancer, the use of IMRT increases the doses that the liver is exposed to incidentally.