Modern society is orientated towards the development of novel, highly-efficient technologies to reduce the negative impact of fossil fuels on the ecology and economy and to provide further sustainable development. Perovskites, materials that have increasingly attracted the attention of scientists since the 1950s due to their specific properties, are still not used on a commercial level. The great potential for their practical use lies in their exceptional electrical, magnetic and catalytic properties. The aim of this work is to investigate whether lanthanum manganite nanoparticles can be synthesized by hydrothermal method and to determine the optimal synthesis conditions. Prepared samples were analysed by thermogravimetric (TGA) and X-ray diffraction analysis (XRD), infrared spectroscopy with Fourier transformation (FTIR) and scanning electron microscopy (SEM). The results of hydrothermal synthesis were compared with the results obtained by coprecipitation synthesis and microwave-assisted hydrothermal synthesis. It is established that in all three cases lanthanum manganite was not formed directly after synthesis, but the obtained precursors had to be annealed. Pure lanthanum manganite was not formed even after annealing, since lanthanum and manganese oxides were also formed. The lanthanum oxide can be removed by dissolution to give pure LaMnO3. The resulting LaMnO3 has a crystallite size in the range 16 – 54 nm, which is twice as small as in the citrate process.