ENThe article presents the recent investigations of two baroque organs attributed to the Vilnius School of Late Baroque Organ Building. The organ in Budslau church in Belarus in Lithuanian’s neighbour (a former part of the territory of the Grand Duchy of Lithuania) has survived in a mostly authentic condition including polychrome paint, wooden and metal pipes, inscriptions on the pipes and console, mechanics etc. In 2014, the records of Jantzon’s signature and date (1781) was discovered inside the organ and finally proved its authorship. The organ in Kurtuvėnai church (Lithuania) was built in 1792-93 and attributed to Jantzon’s follower Raczkowski. However in 1932, the old instrument was replaced by the new one. In 2014, the authentic wooden and metal pipes were found in a room above church sacristy. Their analysis (the identification of tones, stops, inscriptions, shape of the pipes, materiality etc.) enabled the reconstruction of an unknown authentic stoplist. The collected data was compared to already proven Jantzon organs and led to the creation of historically reasoned restoring programmes.