Purpose <p>[¹⁸F]fluorodeoxyglucose (FDG)-PET is a powerful tool to evaluate prognosis in multiple myeloma (MM). The development of systematic and reproducible standard interpretation criteria is crucial for the effective application of FDG-PET in MM. A new set of criteria—Italian Myeloma criteria for PET Use (IMPeTUs)—has standardized PET evaluation in MM. However, the prognostic value of IMPeTUs score remains unknown.</p> Methods <p>A total of 58 patients with newly diagnosed multiple myeloma (NDMM) who underwent both [¹⁸F]FDG-PET/MRI and PET/CT examinations at diagnosis were enrolled (ChiCTR1900022597). All patients completed a 42-month follow-up. The prognostic value of the PET/MRI (or PET/CT) IMPeTUs score in predicting progression-free (PFS) and overall (OS) survival was compared with that of individual laboratory parameters and the maximum standardized uptake value (SUVmax). Kaplan-Meier method was used for survival analysis. Univariate and multivariate analyses of prognostic factors were conducted using Cox regression.</p> Results <p>ROC curves demonstrated that the area under the curve for the PET/MRI IMPeTUs score was 0.760, exceeding that of the PET/CT IMPeTUs score (0.711), PET/CT BM SUVmax (0.649), PET/MRI BM SUVmax (0.575), bone marrow plasma cells (0.500), and β2-microglobulin (0.501). Univariate analysis and Kaplan-Meier analysis showed that a PET/MRI IMPeTUs score ≥ 13 and PET/CT IMPeTUs score ≥ 10 were significantly associated with worse PFS. Cox multivariate analysis showed that a PET/MRI IMPeTUs score ≥ 13 was an independent risk factor for PFS.</p> Conclusion <p>IMPeTUs standardized [¹⁸F]FDG-PET/MRI and PET/CT readings in MM. The IMPeTUs score is crucial for predicting MM prognosis, performing better than SUVmax and clinical indicators.</p> Clinical trial registration <p>ChiCTR1900022597, Registered on 18 April 2019.</p>