Tracer injection into ovarian ligaments has been shown to detect sentinel nodes (SNs) in patients with ovarian cancer. To determine the possibility that SNs are missed, this feasibility study compared their detection during surgery with their detection on postoperative SPECT/CT. Methods: In 8 patients (with either ovarian or endometrial cancer), after a staging lymphadenectomy including resection of SNs related to the ovary, SPECT/CT was performed within 24 h. Results: SPECT/CT identified hotspots in 4 patients at sites where SNs were resected. In 6 patients, additional sites were found, mainly in the pelvic region. Conclusion: Discrepancies between the gamma-probe and SPECT/CT may be due to missed SNs during surgery, but with respect to pelvic hotspots, in most cases they are more probably related to remnants of tracer at injection sites. With respect to sites where SNs were resected, remaining hotspots may have been caused by residual lymphatic flow after resection.