A procedure is proposed to determine the in-plane (a(parallel to)) and out-of-plane (a(perpendicular to)) lattice parameters of [11n] epitaxial cubic strained layers by high resolution X-ray diffraction (HRXRD) rocking curves (RC). The common approach followed to obtain the lattice parameters from asymmetrical diffraction RC of [001] grown films, is extended to apply it to [11n] grown layers. Epitaxial pseudomorphic Ge layers were grown on [001], [110], [111], [112], [113] and [114] GaAs substrates to analyze them by HRXRD. Reciprocal space maps (RSM) were also measured to obtain the lattice parameters of these samples. We observe an excellent agreement of the RC and RSM results, which demonstrates the validity of the suggested RC approach. (c) 2006 Elsevier B.V. All rights reserved.