Ethylene was copolymerized with 1,5-hexadiene (1,5-HD), 1,4-hexadiene (1,4-HD) and 1,7-octadiene (1,7-OD) with bis(2-methyl indenyl) zirconium dichloride/ methylaluminoxane. 1,5-HD units formed the trans-structured cyclopentane rings and I-butenyl side chains, and cross-linking took place during ethylene/1,5-HD (E15HD) copolymerizations. The lower the polymerization temperature was, the larger the amount of hot xylene (XYL)-insoluble faction was. Copolymers of ethylene/1,7-OD (E170D) did not have any cyclic structures and were nearly insoluble in XYL when produced below 60degreesC. In contrast, all the copolymers of ethylene/1,4-HD (E14HD) were completely soluble in XYL. The broadest differential scanning calorimetry melting peak was found for E15HD and then for E170D, and the narrowest was found for E14HD due to the presence or the absence of the cyclic structures and cross-linking. Addition of 1,7-OD or 1,4-HD) as a comonomer reduced the polymerization rate and the molecular weight of the respective copolymers much more than that of 1,5-HD.