Volume measurment of the breast allows for better surgical planning and implant selection in breast reconstructive and symmetrization procedures. The safety and accuracy of tumor removal, in accordance with oncoplastic principles, may be imporved by knowing the true breast- and breast tumor volume. The authors discuss the methods of volume measurement of the breast and describe the method based on magnetic resonance imaging digital volume measurment in details. The volume of the breast parenchyma and the tumor was determined by processing the diagnostic magnetic resonance scans, and the difference in the volume of the two breasts was measured. Surgery was planned and implant selection was made based on the measured volume details. The authors conclude that digital volume measurement proved to be a valuable tool in preoperative planning of volume reducing mammaplasty, replacement of unknown size implants and in cases when breast asymmetry is treated. Orv. Hetil., 2014, 155(11), 407–413.