High-performance Ziegler-Natta catalysts with ill-defined structural hierarchy were studied over multi-length scales. In this study, multilateral characterization was performed to address quantitative structure-performance relationships in ethylene/1-hexene copolymerization with Mg(OEt)(2)-based Ziegler-Natta catalysts. Macroscopic characteristics of the catalysts (e.g., particle size and meso- and macropore volumes) were greatly affected by structures of Mg(OEt)(2) precursor particles, while microscopic characteristics (e.g., micropore volume and chemical composition) were hardly influenced. Ethylene/1-hexene copolymerization results suggested the significance of monomer diffusion: The activity was enhanced for smaller catalyst particles, while the 1-hexene incorporation was improved with larger rneso- and macropore volumes. (C) 2013 Elsevier Inc. All rights reserved.