Simple Summary Radiotherapy plays an important role in the multidisciplinary management of breast cancer. Historically, techniques for radiation treatment of breast carcinomas have been based upon two-dimensional planning and dose application. This treatment has been associated with a relatively high risk of chronic toxicity. Modern radiotherapy techniques have made it possible to achieve a better target volume coverage with a lower critical organ radiation burden. New fractionation methods have led to shorter treatment times while improving the therapeutic ratio. All of this has permitted a reduction in both acute and chronic toxicity, and led to improvements in treatment effectiveness. Currently, partial breast irradiation is used effectively in indicated cases. This can be achieved through utilizing various irradiation techniques and a number of fractionation schemes (e.g., partial breast irradiation and accelerated partial breast irradiation). Problematic issues are related to the application of adjuvant radiotherapy in patients immediately after breast replacement surgery. Modern radiotherapy techniques are designed to permit reduced irradiation of healthy tissue, resulting in a diminished risk of adverse effects and shortened recovery times. Several randomized studies have demonstrated the benefits of increased dosage to the tumor bed area in combination with whole breast irradiation (WBI). Conventional WBI treatment following breast-conserving procedures, which required 5-7 weeks of daily treatments, has been reduced to 3-4 weeks when using hyperfractionated regimens. The dosage administration improves local control, albeit with poorer cosmesis. The method of accelerated partial breast irradiation (APBI) shortens the treatment period whilst reducing the irradiated volume. APBI can be delivered using intraoperative radiation, brachytherapy, or external beam radiotherapy. Currently available data support the use of external beam partial breast irradiation in selected patients. Modern radiotherapy techniques make it possible to achieve favorable cosmesis in most patients undergoing immediate breast reconstruction surgery, and studies confirm that current methods of external beam radiation allow an acceptable coverage of target volumes both in the reconstructed breast and in the regional lymphatic nodes.