Kidney perfusion can be measured using DCE or ASL, but clinical confidence in the assays is undermined by the large variability in published values. In this study, an intra-subject comparison was performed of DCE and ASL against phase-contrast RBF in 25 patients with diabetic kidney disease. Results show that the three techniques agree well on average, but pairwise agreement on the single-subject level remains poor. ASL agreed better with PC than DCE, but the difference was driven by a single DCE outlier. While RBF is a useful biomarker for studies at population level, individual patient management will require further optimization.