PURPOSE: To perform ultrasonographic evaluation of the preoperative status of the posterior vitreoretinal interface in phakic patients undergoing surgery for retinal detachment (RD) with flap tear(s) and to investigate its relationship with postoperative anatomic and visual acuity outcomes. METHODS: A prospective, consecutive case series including 50 phakic eyes of 49 patients with retinal detachment and flap tear(s) undergoing retinal detachment surgery by a single vitreoretinal surgeon, who was unaware of the patient's preoperative B-scan ultrasonographic findings. Main outcome measures were comparisons between patients with partial versus complete posterior vitreous detachment (PVD) of primary retinal reattachment rates (retinal reattachment with a single surgical procedure), rates of retinal reattachment at month 12, and visual acuity outcomes at month 12. RESULTS: Partial PVD was observed in 22 (44%) eyes and complete PVD in 28 (56%) eyes. Eighteen eyes underwent pneumatic retinopexy, 15 underwent scleral buckling, and 17 underwent pars plana vitrectomy. Retinal reattachment with a single surgical procedure was achieved in 76% (38/50) of eyes, including 54.5% (12/22) of eyes with partial PVD at baseline and 92.9% (26/28) of eyes with complete PVD at baseline (P < 0.01). Stratification by type of surgical intervention demonstrated a significantly higher rate of primary anatomic success for pneumatic retinopexy among patients with complete PVD compared to partial PVD (P = 0.02). Retinal reattachment at month 12 was achieved in 100% (50/50) of eyes. At last follow-up, the mean (+/-SD) number of interventions was 1.70 (+/-1.10) for patients with partial PVD at baseline and 1.10 (+/-0.30) for patients with complete PVD (P < 0.01). There was no significant difference among the groups in mean change in visual acuity from baseline to month 12, nor in the distribution of visual acuities at month 12. CONCLUSIONS: In phakic patients with retinal detachment and flap tear(s), a higher primary anatomic success rate may be associated with the presence of a complete PVD compared to a partial PVD. Subgroup analysis suggests that the presence of partial PVD at baseline might influence negatively the primary anatomic success rate, particularly for eyes undergoing pneumatic retinopexy.