Quantitative structure analyses of YBa2cu, O, s thin films, prepared by radio-frequency sputtering and molecular-beam-epitaxy methods, have been carried out with the x-ray-diffraction method. The expansion in c-lattice parameters of the as-grown thin films were found to be caused by one of the following factors or a combination of them: lattice defects introduced during deposition, deficiency of oxygen, and the disordering of Y and Ba atoms. To study phenomena concerning the deficiency of oxygen, further investigations were carried out with the use of experimentally controlled oxygen-deficient thin films with 6 values ranging from 0.07 to close to 1.0. Systematic changes in the c-lattice parameters and diffraction intensities with increasing 5 were observed; also, a very convenient method for the quantitative determination of oxygen content in the thin films determined from the ratio of the integrated intensity of 005 to 006 reAections has been established. Structure analyses of the oxygen-deficient thin films revealed that the oxygen dependence of the structural parameters in the thin films are similar to that reported for bulk samples. Electrical-resistivity measurements showed that the thin films exhibit clearly a "two-plateau" T, versus 6 behavior.