We investigated the impact of contrast media (CM) with different osmolality on cardiac preload in patients with chronic kidney disease (CKD) and congestive heart failure (CHF). Patients with CKD and CHF were equally randomized to receive either iso-osmolar contrast media (IOCM) iodixanol or low-osmolar contrast media iopromide. We measured cardiac preload indexes by invasive hemodynamic monitoring before and after CM injection. Major adverse cardiac events postprocedures were recorded. Increase in extravascular lung water index was only seen in the iopromide group (P < .001), while global end diastolic index and central venous pressure were all significantly increased from baseline in the both groups (P < .001, respectively), and the increase in cardiac preload indexes was significantly greater in the iopromide group than in the iodixanol group (P < 0.001). The overall incidence of acute heart failure was more frequently observed in the iopromide group (P = 0.027). Low-osmolar contrast media iopromide significantly increased cardiac preload in patients with CKD and CHF undergoing cardiac catheterization procedures compared with IOCM iodixanol.