Adsorption of cis-2-butene and trans-2-butene on clinoptilolite-rich tuff and ion-exchanged forms was investigated. Clinoptilolite samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, chemical analysis and nitrogen adsorption techniques. Adsorption isotherms for cis and trans 2-butene on purified clinoptilolite (Cp) and modified forms (Na-Cp, K-Cp, Ca-Cp and Mg-Cp) were obtained at pressures up to 2.7 atm. and at 25°C. The results show that natural clinoptilolite has a considerable potential for separation of the two hydrocarbons. Mg-Cp samples showed maximal uptake of both cis-2-butene and trans-2-butene.