[en] Various analytical procedures for the determination of both macro- and trace amounts of lanthanum in praseodymium oxide by neutron activation analysis were elaborated. Non-destructive gamma-ray spectrometry with scintillation NaJ(Tl) detectors was used for the determination of macro amounts of lanthanum. The precision of determination depended considerably upon the method used for the evaluation of digital data from pulse height analyser, and improved in the series: classical Covell's method, Sterlinski's method, and SONA computer program. Lanthanum content that could be determined by this method ranged from several percent down to 5x10^-3%. Trace amounts of La were determined both non-destructively by high resolution gamma-ray spectrometry with Ge(Li) detector and by radiochemical method in which lanthanum traces were isolated by ion exchange chromatography and finally determined by gamma ray spectrometry with NaJ(Tl) detector. Radiochemical method was found to be more accurate and precise. Lower limit of detection was estimated to be approximately 7x10^-6%. (author)