We present experiments on the melt and crystal morphology of a asymmetric semi-crystalline poly(ethylenelbutylene-b-ethyleneoxide) diblock copolymer (PBh-b-PEO) in bulk as well as in thin films. Simultaneous small- and wide-angle X-ray scattering combined with AFM and TEM images reveal in the melt a bulk morphology of hexagonally packed cylinders of PEO in a PBh matrix, that transforms into a hexagonal perforated lamellar phase upon crystallization. X-ray reflectivity of thin films of PBh-b-PEO in the melt indicates wetting layers at the top and bottom inter-faces, which force the cylinders in the interior to orient parallel to the substrate. Crystallization of the PEO block leads to roughening of the air/film interface and causes lateral structuring coexisting with planar lamellar layers in thinner films. (c) 2005 Elsevier Ltd. All rights reserved.