Introduction & Objective: Breast ASYMMETRY and chest wall ASYMMETRY are common but there is no comprehensive classification and relative distribution in the research literature. This ASYMMETRY can be caused by various issues such as diseases, abnormalities and complications of surgery. The aim of this study was to investigate the chest wall ASYMMETRY and its effects on breast ASYMMETRY. Materials & Methods: In this cross-sectional study, which was performed retrospectively, the records of patients applying for mammoplasty from 2013 to 2020 were reviewed. Preoperative frontal imaging is performed on these patients. The frontal photograph of the breast and chest was examined before the operation. Distance between right nipple to midline of chest, distance between left nipple to midline of chest, length of right midclavicular distance to right nipple and length of left midclavicular distance to left nipple, right chest width, chest width Left breast, sternal notch distance to right nipple and sternal notch to left nipple distance were calculated by software and analyzed using chi-square test. Results: Based on the results obtained in measuring chest wall width and nipple to midline distance, 256 cases (56. 4%) and 283 cases (62. 3%) of the left breasts were larger, respectively. In nipple to ant axillary line measurements, the frequency of people with a larger right was higher. In the chest wall width variable, only in the prosthesis group, there was a statistically significant difference between left and right size (P-value <0. 05). There was a statistically significant difference between left and right size in nipple to midline distance and nipple to ant axillary line variables (P-value <0. 05),But in SNN variable, there was no statistically significant difference between left and right size in any of the groups (P-value >0. 05). Conclusions: Based on the results, the breast and chest wall ASYMMETRY is common. Therefore, patients should be reminded that due to the difference in the width of the chest and breast on both sides and their ASYMMETRY, this ASYMMETRY will also exist after breast cosmetic surgery. This influences decisionmaking and planning to reduce this ASYMMETRY using surgical and non-surgical methods.