A potential recycling rout for the end-of-life cathode ray tubes (CRT) is its application as a fluxing material in lead and copper smelting processes. Therefore, a thorough study on possible effects of the additional CRT on products and by-products of the metallurgical operation is required. In this paper, influences of CRT addition on mineralogy and leaching behaviour of a fayalite-type slag from a Swedish copper producer are investigated. Mixtures of slag/CRT, in different fractions, were prepared and re-melted in a Tamman furnace. Materials characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and standard leaching tests were done for all samples. Results depict that the main crystalline phase of the slag does not change due to CRT addition. By 10 wt-% CRT addition, leachability of major elements decreases; whereas, that of some minor elements increases. With 35 wt-% CRT addition, leaching of some environmentally detrimental elements make the material unacceptable for construction purposes according to the regulations.