PURPOSE: To report and compare the incidence of pupillary capture and posterior synechiae formation after combined cataract extraction and pars plana vitrectomy (PPV) with a 1-piece versus a 3-piece acrylic intraocular lens (IOL). SETTING: Royal Alexandra Hospital Eye Clinic, University of Alberta, Edmonton, Alberta, Canada. DESIGN: Comparative case series. METHODS: Consecutive patients who had combined cataract extraction with PPV were retrospectively reviewed. The outcomes in patients who received a 1-piece acrylic IOL and those who received a 3-piece acrylic IOL were compared. The proportion of patients with pupillary IOL capture and/or posterior synechiae postoperatively was recorded. RESULTS: The cohort comprised 145 patients. All cases of IOL capture occurred in eyes with a 1-piece IOL (n = 7; 7.7%); the difference between the 1-piece IOL group and the 3-piece IOL group was statistically significant (P = .043). There was no significant difference between the 2 IOL types in the rate of posterior synechiae formation. Regression analysis showed that the odds of posterior synechiae formation were significantly higher in cases in which perfluoropropane (C(3)F(8)) (odds ratio [OR], 24.01; P = .006), sulfur hexafluoride (SF(6)) (OR, 25.23; P = .007), or silicone oil (OR, 47.78; P<.001) was used. CONCLUSIONS: The incidence of IOL capture was significantly greater after implantation of a 1-piece IOL than after implantation of a 3-piece IOL during combined cataract extraction and PPV. Posterior synechiae formation was associated with the use of silicone oil, SF(6), or C(3)F(8).