Single crystals of syndiotactic poly(propene-co-l-butene) with l-butene as the rich component have been obtained through ultrathin film growth from the melts. The morphological and structural studies on these single crystals have disclosed the influence of propene units on the crystallization behavior of syndiotactic poly(l-butene) (sPB-1). Bright field electron microscopy shows that incorporating the propene units in the sPB-1 chains influences the crystallization habit of the sPB-1 significantly. For example, the aspect ratio of the single crystals increases with increasing the propene units, resulting in copolymer single crystals more similar to those of the sPP homopolymer. The electron diffraction results indicate that a small amount of propene units, up to 9-10 mol%, does not affect the C-centered chain packing of form I of sPB-1. The propene units are most likely included into the crystalline structure of sPB-1. For much higher propene content, around about 30 mol%, the b/4 shift disorder takes place. Nevertheless, the C-centered chain packing is still the predominant packing scheme in the single crystals of the l-butene-rich copolymers, even though with substantial amount of disorder.