The morphology and the strain relaxation of a laterally patterned GaAs/Ga0.86In0.14As/GaAs surface wire structure on GaAs [001] were studied before and after the MBE-overgrowth with Ga0.9Al0.1As by use of two different X-ray diffraction methods. Whereas the coplanar high-resolution X-ray diffraction (HRXRD) provides the shape and both components of the strain tensor but averaging over the whole vertical structure, the depth variation of shape and of the in-plane component of the strain tensor become available using the non-coplanar grazing incidence diffraction (GID) technique. The latter method is favored for non-destructive analysis of buried lateral structures. At freestanding surface grating the evaluated strain components indicate an inhomogeneous relaxation profile of wires which is induced by the GaInAs single quantum well. Additional strain components have to be attributed to non-periodic defects caused by the preparation process. At the buried structures we found in-plane strain release within the wires and periodic modulated in-plane strain within the 150-nm thick GaAlAs overlayer accompanied with a periodic modulation of the Al-content. Taking into account recent investigations at low strained material the strength of the induced compositional modulation is driven by the initial strain state of the wire structure. Beside that we found additional strain components which we attribute to a non-periodic Al-segregation.