OBJECTIVE. The purpose of this study was to compare gradient-recalled echo (GRE) with spin-echo (SE) MR imaging in the assessment of vessel patency and tumor margins in children with intraabdominal tumors. MATERIALS AND METHODS. Findings on GRE and SE images in 10 children with abdominal neoplasms were retrospectively evaluated and compared with pathologic findings or results of CT studies. RESULTS. Detection of tumor thrombus was 100% with GRE sequences and 75% with SE sequences. The SE sequences yielded two false-positive diagnoses of tumor thrombosis, whereas the GRE sequences yielded no false- positive or false-negative diagnoses. In patients with extrinsic compression of the inferior vena cava by tumor, GRE images were consistently better than SE images for confirming vessel patency. GRE images also were superior to SE images at showing flow in mesenteric vessels, renal arteries, and renal veins. However, GRE images displayed tumor margins less well than SE images did, and they were also more susceptible to ghosting artifacts. CONCLUSION. Our results suggest that the GRE sequence is a useful adjunct to SE sequences for evaluating vascular involvement in children with abdominal tumors.