Hydride vapour phase epitaxial GaN layers with thicknesses in the range 10-150 mum grown directly on sapphire or using metalorganic vapour. phase deposited GaN templates have been separated by laser-induced lift-off technique. Both faces of the free-standing films have been studied by photoluminescence and high-resolution X-ray measurements and stress analysis has been performed. A comparison with as-grown films reveals the changes in the properties of the material after the separation process. The separation conditions are found to be responsible for the bowing in the freestanding GaN films while:the type and intensity of emission bands, as well as defect and impurity distributions are related only to the growth; conditions. The residual strain in the free-standing layers is attributed to both non-optimized separation conditions and non-uniform defect density. in the films. (C) 2002 Elsevier Science B.V. All rights reserved.