Lattice defects present in PLD-grown, epitaxial SrRuO3 thin films on (001) SrTiO3 substrates are analyzed by high resolution transmission electron microscopy (HRTEM). Before the preparation of TEM samples, the electrical resistivity of films grown at different substrate temperatures was determined. Films grown at 775 °C exhibited a low electrical resistivity of only 200 μΩcm. They were found to be of orthorhombic structure and contained only few lattice defects. Films grown at 700 °C showed a high electrical resistivity of 1400 μΩcm. They were of cubic lattice symmetry, while films grown at temperatures above 800 °C showed resistivities between 300 and 900 μΩcm. The latter films mainly consist of an orthorhombic-cubic phase mix and involve lattice defects of high density, such as twins and antiphase boundaries (APBs). These defects are mainly located in between the islands and obviously contribute to the high film resistivity observed. For example, the APBs contain an extra single SrO layer, which is certainly insulating. Moreover, Ru vacancies are present in these films.