4-Methoxy-2-methylbenzoates of Y(III) and lanthanides(III) (La-Lu) were prepared as crystalline anhydrous complexes with general formula Ln(C9H9O3)(3) (complexes of La and Pr as monohydrates). Monohydrates heated in air lose crystallization water molecule and then anhydrous complexes decompose directly to oxides. Only La(III) complex decomposes to oxide with intermediate formation La2O2CO3. The carboxylate group in the studied complexes is a tridentate chelating-bridging or bidentate chelating (Y).