Purpose: The use of three-dimensional (3D) breast volume assessment methods is gaining popularity in the field of breast surgery. The Vectra® XT 3D system has been reported in the literature to produce volumetry with good correlation with mastectomy specimen and for preoperative patient counselling. We present our analysis of Vectra® XT 3D volumetry relative to Breast MRI with consideration to ptosis. Methodology: Study population was drawn from women who underwent Breast MRI as part of a high-risk screening program. A study radiologist performed MRI volumetry. The automatic preset function on the Vectra Mirror® program was used for 3D volumetry. Ptosis was recorded using the Regnault classification after reviewing 2D photographs of the subject breasts. Pseudoptosis was not assessed. Results: 106 breasts from 53 women demonstrated no or minimal ptosis (grades 0-1) in 77 cases and mod-severe (grades 2-3) in 29 cases. Mean breast volumes for mod-severe ptotic breasts (grade 2-3) were 1019cc and 732 cc via MRI and Vectra Mirror® respectively. Pearson correlation for MRI and Vectra volumetry for no/minimal ptosis and mod-severe ptosis were 0.872 and 0.814, respectively. Both median (75 vs.280cc) and IQR (227 vs.498cc) for the difference between MRI and Vectra volumes were larger in mod-severe ptosis on Boxplot analysis. Conclusion: When measuring breast volume for reconstructive surgery, it can be challenging for surgeons, especially with breast ptosis. The correlation between different methods diminishes with higher degree of ptosis. Further study is required in a larger population with mod-severe ptosis and controlled for age and BMI to confirm these findings.