Abstract: Objective: This study aims to compare and summarize the imaging features of enhanced computed tomography (CT) and plain magnetic resonance (MR) in the examination of pseudomyxoma peritonei, and evaluate the diagnostic value of their combined application. Methods: Imaging data from 20 patients with pathologically confirmed appendiceal-derived pseudomyxoma peritonei were retrospectively collected. Two senior radiologists reviewed the enhanced CT and plain MR images in a double-blind manner, analyzing imaging signs, such as mucinous ascites, omental cake sign, peritoneal cancer index (PCI) score, calcification foci, primary lesion, lesion septa, and scallop sign. was used to score the diagnostic confidence for enhanced CT, plain MR, and their combination was assessed using a 5-point Likert scale. Results: Good agreement was observed between the two observers in the assessment of imaging findings. CT demonstrated superior visualizations of calcification, enhancement of primary lesions, and the scallop sign, whereas MRI showed greater efficacy in detecting peritoneal microimplants, lesion segmentation, and differentiating mucinous ascites. The peritoneal cancer index evaluated using both methods was highly correlated with the intraoperative results (CT: r=0.940, RMSE=4.68; MRI: r=0.988, RMSE=1.90). When the two methods were combined, the average diagnostic confidence score across all features was the highest (5.00), particularly for PCI and primary lesions, and exceeded that achieved with either method alone. Conclusion: Enhanced CT and plain MR resonance imaging have complementary effects in the diagnosis of pseudomyxoma peritonei. Their combined use can improve the diagnostic confidence and provide a more accurate and reliable imaging basis for individualized treatment.