PLZT 4/65/35 thin films were prepared by the acetic acid based sol-gel route. The choice of lanthanum precursor, i.e., acetate or nitrate, influences the functional group content of formamide modified sols and the microstructure of the thin films. The lanthanum nitrate based PLZT thin film deposited on Si/SiO2/TiO2/Pt/TiO2 substrate has a columnar perovskite grain structure, while the lanthanum acetate based one is characterized by a lead-silicon containing reaction layer beneath the platinum electrode. Although lead is depleted from the PLZT thin film the perovskite structure is retained by the use of the top layer with a large excess of PbO.