Purpose: To evaluate the difference between the predicted and actual postoperative refractions after combined vitrectomy and cataract surgeries with a posterior capsulectomy. Methods: We performed a retrospective study of 33 eyes of 33 patients who underwent combined vitrectomy and cataract surgeries in our hospital between March 2013 and May 2014. The patients were divided into 2 groups: those who underwent a posterior capsulectomy (group A) and those who underwent combined vitrectomy and cataract surgeries (group B). The actual refractive errors were analyzed 3 months after surgery using spherical equivalent. We compared the results between the predicted and actual refractive errors in the two groups. Results: Group A consisted of 25 eyes of 25 patients and group B of 8 eyes of 8 patients. In group A, the average difference between predicted and actual postoperative refractive errors was -0.16 ± 0.38 D (p = 0.083). The predicted refraction was -0.33 ± 0.46 D and actual refraction was -0.49 ± 0.55 D in group A. There was no statistically significant difference between the predicted refraction and actual refractive errors in group A (p = 0.083). In group B, the average difference between predicted and actual postoperative refractive errors was 0.27 ± 0.29 D (p = 0.078). Additionally, the predicted refraction was -0.49 ± 0.77 D and actual refraction was -0.22 ± 0.59 D. The difference between the predicted refraction and actual refractive errors in group B was not statistically significant (p = 0.078). Conclusions: When a posterior capsulectomy is performed during combined vitrectomy and cataract surgery, no significant difference in refractive errors between the predicted refraction and actual refractive errors was observed 3 months after surgery. Compared with combined vitrectomy and cataract surgeries only, a small amount of myopic refractive change tended to occur 3 months after surgery. J Korean Ophthalmol Soc 2015;56(5):709-714