Crystallization of polymer chains between hard glassy walls or between amorphous domains in a nanoscale lamellar structure has been observed using simultaneous small-angle and wide-angle X-ray scattering (SAXS/WAXS). Semicrystalline symmetric diblock copolymers containing poly(ethylene) (PE) and a room-temperature glassy or amorphous component were shear oriented in the high temperature lamellar melt, then quenched below the PE melt temperature. For the glassy sample, the orientation of chain-folded PE stems was deduced from SAXS/WAXS peak positions to be parallel to the lamellar interface-Diffuse scattering bars consistent with lateral positional correlations of the PE crystallites were observed only in the SAXS patterns for the glassy sample with the X-rays incident parallel to the lamellae. In contrast, in a sample containing amorphous lamellae, PE crystallization occurred with weak crystallite orientation and no lateral positional correlations of crystallites.