The defect concentrations in lanthana substituted lead titanate and the effect of sintering temperature on the dielectric constant (e‘) around the Curie point have been studied. On the basis of our x-ray diffraction results the presence of Ti-site vacancies seems unlikely. This conclusion is in contradiction with Hennings’ defect model. A decrease of the sintering temperature leads to a decrease of the maximum value of e and to a broadening of the peak in the e‘ vs. temperature curve at the Curie point. Probably, grain size as well as compositional fluctuations contribute to the observed variations.