The competitive binding of Cd and Zn from equimolar binary aqueous solution of total initial concentration of c o (Cd+Zn) ≈ 1 mmol/L is performed. The process is carried out in a glass column filled with fixed bed of natural zeolite of height 8 cm at the solution flow rates of 1, 2, 3 and 4 mL/min. The service cycle is monitored by determining the concentration of Cd and Zn and pH values in the effluent. The results are shown by breakthrough curves for each ion from which the breakthrough and exhaustion points are determined. By increasing in flow rate, the breakthrough appeared earlier, and approximately equal volume of solution is treated for significantly shorter time. Cd and Zn bind simultaneously until the breakthrough, for all examined flow rates. After the breakthrough, the concentration of both ions in the effluent suddenly increased, but the Cd concentration is lower than the Zn concentration. Also, the concentration of Cd in the effluent does not exceed the influent concentration, while Zn overshoots its influent concentration, but only for the lowest flow rate of 1 mL/min. The reason for this is the displacement of already bound Zn from the zeolite structure by Cd from the inlet solution due to greater selectivity of the zeolite clinoptilolite towards Cd and higher affinity of Cd toward zeolite. At higher flow rates, due to the faster solution flow through the layer, the displacement effect is less pronounced due to the shorter contact time and lower diffusion of Cd and Zn from the solution into the zeolite particle. The ratio of capacities for Cd and Zn in breakthrough equals to the Cd/Zn ratio in the influent, which confirms the simultaneous binding of Cd and Zn to the breakthrough, proportionally to their concentration in the inlet solution. The ratio of capacities in exhaustion is greater than the Cd/Zn ratio in the influent, confirming the displacement effect of Zn by Cd. At reduced contact time with increased flow rate the column efficiency η decreases. The obtained results showed higher affinity of Cd for zeolite than Zn, as well as greater selectivity of zeolite toward Cd, and thus better binding of Cd for all examined flow rates. This was not expected since Cd and Zn ions have very similar physical-chemical properties, which makes these results as very important for predicting of zeolite behaviour and its practical application in water treatment processes.