A geochemical approach combining chemical and mineralogical studies together with pH-dependent leaching experiments was applied to carry out an environmental risk assessment analysis of copper metallurgical slags. Two groups of Cu-metallurgical slags were investigated: historical (HS) and modern slags including shaft furnace slag (SFS), granulated slag (GS) and lead slag (LS) representing various smelting technologies. The metallic elements composition (Cu, Zn and Pb) of the slags, especially their distribution in mineral phases as well as their leachability at different pH conditions were determined. The slags display different chemical (e.g., Cu; HS: 5657mg/kg; SFS: 2687mg/kg; GS: 11,425mg/kg, LS: 10,915mg/kg) and phase composition, with various impurities of metallic elements in different quantities. Consequently, these materials show different leachability of metallic compounds when exposed to various pH conditions (2-13). HS and SFS slags are mainly composed of synthetic analogues of silicates such as fayalite (HS) and diopside (SFS) as well as minor sulphides. GS is an amorphous material composed of glass containing copper droplets, whereas LS is an exceptional slag type corresponding to a matte and characterized by a volumetrically major sulphides and a minor fayalite content. pH-dependent leaching experiments revealed that high concentrations of Cu, Zn and Pb may be released during leaching. Aggressive acidic conditions (pH2) were found to be the least stable for the analysed materials, e.g., Cu: up to 5873mg/kg for GS; Zn: up to 8919mg/kg for LS, Pb: up to 17,186mg/kg for LS. Alkaline pH (12-13), being generally less aggressive for slags than acidic conditions, also showed that significant amounts of metals may be mobilized (e.g., Cu: up to 114mg/kg for HS; Zn: up to 243mg/kg for LS; Pb: up to 5539mg/kg for LS). pH conditions close to neutral (7-8) and those with slightly alkaline pH (10.5) appear to be the most stable for the analysed materials.