Although three-dimensional (3D) simulations are becoming more common in preoperative breast augmentation planning, this does not necessarily imply that the simulated results are highly accurate. We aimed to evaluate the accuracy of the 3D simulation technique by comparing the differences in breast morphology between the 3D prediction model and the actual results. The simulation and actual postoperative results of 103 patients who underwent breast augmentation were analyzed retrospectively. Therefore, a 3D model was created, and the parameters of line spacing, nipple position, breast projection, surface area, and volume were evaluated. Furthermore, consider the difference in chest circumferences and breast volume. In comparison with the simulation results, the actual results had a mean increase in the nipple to the inframammary fold (N-IMF) of 0.3cm (P < 0.05) and a mean increase in basal breast width (BW) of 0.3cm (P < 0.001), a difference that was not statistically significant in patients with larger breast volumes. There was a significant difference in the mean upper and lower breast volume distribution between simulated and actual breasts (upper pole 52.9% vs. 49.2%, P < 0.05, and lower pole 47.1% vs. 50.8%, P < 0.001). However, it was not statistically significant in patients with larger chest circumferences. Our study shows that 3D simulation has uncertainties related to the patient's chest circumference and breast volume. Therefore, these two critical factors must be considered when using simulation assessment in preoperative planning. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .