Since 2002, twenty-five patients affected by breast cancer, for whom extensive lung/heart involvement was expected from conventional techniques, were irradiated with intensity modulated photon beams (IMRT). For 10 patients the internal mammary lymphatic chain was included in the target, 6 patients received treatment of the thoracic wall after mastectomy and 9 patients were treated after breast conserving surgery. Dose prescription ranged between 48.6 and 50 Gy at 1.8 or 2 Gy per fraction. The target volume (PTV) ranged from 194 to 2121 cm3. For all cases a Dose Volume Histogram analysis has been conducted on omolateral lung, heart, contralateral lung and breast, healthy tissue and PTV. For PTV the volume receiving more than 90% of the prescribed dose (V90%) was 95.8+/-1.8% while V107% = 5.3+/-2.8%. The mean dose computed for the heart was 10.4+/-2.9 Gy, for the omolateral lung: 13.3+/-2.8 Gy, for the contralateral breast: 3.4+/-1.8 Gy, for the contralateral lung: 4.6+/-2.7 Gy. For the omolateral lung V20Gy = 23.1+/-7.0% and V45Gy = 0.8+/-0.9 Gy. With a short mean follow up of 10.4 months, no pulmonary or cardiac complications were observed. IMRT proved to be technically feasible on a clinical basis for the treatment of the whole breast, including internal mammary chain, or of the thoracic wall after mastectomy.