Contrast‐induced nephropathy (CIN) is considered to result from intrarenal vasoconstriction, and occurs more frequently in impaired than in normal kidneys. We hypothesised that iodinated contrast media would markedly change renal blood flow and vascular resistance in functionally impaired kidneys. We enrolled 36 patients (32 men; mean age, 75.3 ± 7.6 years) undergoing diagnostic coronary angiography and divided them into two groups based on the presence of chronic kidney disease (CKD), defined as an estimated glomerular filtration rate (eGFR) of < 60 mL/min/1.73 m2 (CKD and non‐CKD groups, n = 18 in both). Average peak velocity (APV) and renal artery resistance index (RI) were measured by Doppler flow wire before and after administration of the iodinated contrast media. APV and RI were positively and inversely correlated with the eGFR at baseline, respectively (APV: R = 0.545, P = 0.001; RI: R = ‐0.627, P < 0.001). Mean RI was significantly higher (P = 0.015) and APV was significantly lower (P = 0.026) in the CKD than in the non‐CKD group. APV (P < 0.001) and RI (P = 0.002) were significantly changed following contrast media administration in the non‐CKD group, but not in the CKD group (APV: P = 0.258; RI: P = 0.707). Although renal arterial resistance was higher in patients with CKD, but not affected by contrast media administration, suggesting that patients with CKD could have an attenuated response to contrast media. This article is protected by copyright. All rights reserved.