Background Identification of the original site of sinonasal inverted papillomas (SIPs) is difficult but essential for reducing the recurrence rate. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) may provide information about tissue perfusion and permeability to solve this problem. Purpose To investigate the accuracy of DCE-MRI parameters in discriminating between regions of interest (ROIs) in the original site and peripheral portion. Study Type Retrospective. Population Ninety consecutive patients with pathologically proven SIP. Field Strength/Sequence 3.0T/DCE-MRI using fast-spoiled gradient recalled (FSPGR) T-1-weighted images with fat saturation. Assessment ROIs were placed in the original site and the peripheral portion of SIP by two radiologists according to surgical records. Maximum slope of increase (MaxSlope), contrast-enhancement ratio (CER), bolus arrival time (BAT), initial area under the signal intensity-time curve (IAUGC), volume transfer constant (K-trans), volume of the extravascular extracellular space (v(e)), and rate constant (K-ep) were calculated and repeated again with a month interval by a radiologist. Statistical Tests Univariate and multivariate analysis was used to determine the best diagnostic parameters, and their performances in discrimination were evaluated by receiver operating characteristic (ROC) curves. Reproducibility was estimated by the intraclass correlation coefficient (ICC). Results MaxSlope, CER, IAUGC, K-trans, and v(e) were significantly lower (P < 0.05) in the original site than the peripheral portion of SIPs. CER (odds ratio [OR] = 0.227, 95% confidence interval [95% CI] = 0.073-0.704) and v(e) (OR = 0.048, 95% CI = 0.004-0.527) were the best indicators for identifying the original ROIs. The combination of CER and v(e) had the best diagnostic performance in the discrimination between the ROIs (the area under the curve [AUC]: 0.937; 95% CI: 0.896-0.974). Data Conclusion DCE-MRI derived parameter values differed between the original site and the peripheral portion of SIPs. The model combining CER and v(e) appears to be able to accurately distinguish the original from peripheral ROIs. Level of Evidence 4 Technical Efficacy Stage 2