OBJECTIVE:Mastectomy is known to effect body posture after a change in the center of gravity of women due to a missing breast. Although previous studies on short-term postural changes in mastectomy patients using photogrammetry or Moiré topography suggested ipsilateral inclination of the trunk, our clinical observations during breast reconstruction surgeries indicated a contralateral shoulder elevation in women with unilateral mastectomy. Because the change in body posture can affect spinal alignment, we aimed to evaluate the long-term physical effects of unilateral mastectomy on spine deformity by radiographic examination. METHODS:Posteroanterior chest radiographs of 60 women (mean age 56.3 ± 8.5 years) taken before and 12 months after the mastectomy were evaluated for Cobb angle and the presence or absence of a tilt from the midline in the coronal plane of vertebral body alignment. RESULTS:Cobb angle decreased in 14 and increased in 38 of 60 patients after unilateral mastectomy, and the angular change was found to be independent of the mastectomy side (P < .001). A shift in Cobb angle to the mastectomy side was observed in 11 of 53 patients (P > .05), whereas a statistically significant shift in Cobb angle to the opposite of the mastectomy side was observed in 33 of 53 patients (P < .001). The results of this observational retrospective study indicated long-term spinal deformation in women with unilateral mastectomy. Two patients with idiopathic scoliosis before mastectomy even developed scoliosis. CONCLUSION:We recommend informing the patients of the possible change in body posture in the long term, which should be supported or limited with physical therapy.