Purpose:To investigate the role of gadolinium enhanced MR imaging in the evaluation of gestational trophoblastic tumors(invasive mole and choriocarcinoma). Materials and Methods:Pre-enhanced T1-and T2-weighted images and gadolinium enhanced T1-weighted images of 34 gestational trophoblastic tumors (15 choriocarcinoma, 19 invasive moles) were retrospectively evaluated ad enhancement paterns were analyzed. Morphologic differences and structural characteristics were analyzed by the evaluation of tumor margin, patterns of heorrhagic necroses, the development of intratumoral vascularity, and molar villi. Graded scores of MR findings between pre- and gadolinium enhanced images were based on the following criteria:1) visualization of tumor margin;2) distinction between tumor necrosis and zone of trophoblastic proliferation;and 3) molar villi. Statistical differences between graded scores of pre-and post-enhanced images were analyzed. Results:A choriocarcinoma was a well-defined mass with peripheral rim enhancement and central hemorrhagic necrosis, while an invasive mole was a ill-defined mass with partial necrosis, tiny cystic areas and increased intratumoral vascularity with dense reticular enhancement. Interface between tumor necrosis and the zone of trophoblastic proliferation was better visualized on gadolinium enhanced images than on pre-enhanced images. Only in invasive moles were tumormargin and intratumoral molar villi clearly discrimated on gadolinium-enhanced images. There was no statistical difference in the visualization of tumor margin of choriocarcinoma between pre-and post-enhanced images. Conclusion:Gadolinium enhanced MR imaging was helpful for the visualization of tumor characteristics in gestational trophoblastic tumors and in differential diagnosis between invasive mole and choriocarcinoma.