Several high T, superconducting (HTSC) YBa2CU3O7-delta films deposited on different substrates by liquid phase epitaxy (LPE) method (LaAlO3 perovskite and MgO) have been characterized by means of selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). In some cases, buffer layers were used. Moreover, another YBa2CU3O7 - delta film was deposited using a SmBa2CU3O7 - delta nucleation layer. Different microstructures were observed, showing several kinds of structural defects, such as twinning, bending of the planes, stacking faults and amorphized domains. Epitaxy was obtained when LaAlO3 perovskite type substrate was used. (C) 2004 Elsevier B.V. All rights reserved.