Objectives <p>To assess renal perfusion and ectopic fat deposition in patients with type 2 diabetes mellitus (T2DM), and to evaluate the effects of ectopic fat deposition on renal hemodynamics.</p> Methods <p>All participants underwent quantitative magnetic resonance imaging (MRI) to measure the cortical and medullary renal blood flow (RBF) and proton density fat fraction (PDFF). Patients with T2DM were classified into three groups according to the estimated glomerular filtration rate (mL/min/1.73 m²). One-way analysis of variance was used to assess differences among groups. Pearson’s correlation coefficient was used to analyze correlations. Additionally, a receiver operating characteristic (ROC) curve was constructed to assess diagnostic performance.</p> Results <p>Renal PDFF values of the renal cortex and medulla, as well as perirenal fat thickness, were significantly different among the four groups: healthy control &lt; T2DM &lt; diabetic kidney disease (DKD) I–II &lt; DKD III–IV. Additionally, significant differences in cortical and medullary RBF values were observed among the four groups: healthy control &gt; T2DM &gt; DKD I–II &gt; DKD III–IV. A significant negative correlation was observed between renal PDFF and RBF values. Medullary RBF values demonstrated the best performance in discriminating T2DM from DKD with the largest area under the ROC curve (AUC) of 0.971. The cortical PDFF achieved the largest AUC (0.961) for distinguishing DKD I-II from DKD III–IV.</p> Conclusions <p>Quantitative MRI effectively evaluates renal perfusion and ectopic fat deposition in T2DM patients, aiding in assessing kidney function and disease progression. Additionally, renal ectopic fat deposition may be an important risk factor for renal hemodynamic injury.</p> Critical relevance statement <p>Quantitative MRI could serve as a radiation-free imaging modality for assessing renal perfusion and ectopic fat deposition, which may be an important risk factor for DKD progression.</p> Key Points <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Quantitative MRI can be used to assess kidney function and monitor disease progression in patients with T2DM.</p> </ItemContent> <ItemContent> <p>In patients with T2DM, decreased renal perfusion, increased renal ectopic fat deposition, and kidney damage were significantly correlated.</p> </ItemContent> <ItemContent> <p>Renal ectopic fat deposition may be an important risk factor for renal hemodynamic injury.</p> </ItemContent> </UnorderedList></p> Graphical Abstract <p></p>