The morphologies of 1-octene-based linear low-density polyethylenes (LLDPEs) prepared with single-site (ss) or Ziegler-Natta (ZN) catalysts were investigated using solid-state C-13 NMR spectroscopy. For each type of LLDPE, two samples, containing either approximately 10 or approximately 30 hexyl branches per 1000 backbone carbons, were studied. Mass fractions of their crystalline and amorphous phases as well as the interphase were quantified; a significant amount of LLDPE exists in the interphase for both types of samples, with their relative amounts decreasing with increasing branch content. Hexyl branches are approximately evenly distributed between the two noncrystalline phases for all samples except the high branch content ZN LLDPE, whose branches tend to cluster in the amorphous phase. The latter observation is attributed to the fact that most of the branched molecules in ZN LLDPE are in the low molar mass fraction and when the branch content is high these chains cannot fold into ordered structural units. The crystalline phase consists of three components with distinct C-13 spin-lattice relaxation, T-1, times; the degree of crystallinity decreases with increasing branch content. For samples with similar branch contents, ZN LLDPE tends to have thicker lamellae than does ss LLDPE.