Pristine CNTs and open-ended CNTs were used as supports for CP2ZrCI2. The effects of the structure of the supports on the activity of the catalyst in ethylene polymerization and the resulting PE morphology were studied. It was found that the two supported catalysts had similar activity. The SEM studies proved that the resulting PE prepared with pristine CNT-supported catalyst exhibited fibrous morphology, while the other PE mainly exhibited fractional morphology. The possible formation mechanism of these two kinds of morphology was proposed. (c) 2006 Elsevier B.V. All rights reserved.