Ethylene and butadiene are copolymerized with neodymocene catalysts. In this paper, a complete H-1 and C-13 NMR analysis of ethylene/butadiene copolymers is reported for the first time. The results of this study show that the microstructure of copolymers depends on the cyclopentadienyl ligands of the catalyst. The presence of the trans-1,2-cyclohexane structure, formed by intramolecular cyclization, is detected and fully investigated by 2D NMR H-1/C-13 direct and long-range correlation.