The importance of Anton Reicha as a pedagogue and music theorist will stand out especially if we focus on the next generations who were influenced by the author, by his theoretical writings. It is little unexpected, that we will find the legacy of Anton Reicha also in theoretical works of Leoš Janáček – a Moravian composer of the 2nd half of the 19th and 1st third od the 20th century. Janáček's theoretical work, which is just a segment of Janáček's comprehensive creative contribution, is a wide-ranging and multi-layered legacy, capturing opinions, professional interests, aesthetic positions and composer's intentions of the author. The character of the occurrence of moments, where Reicha is in the Janáček's theoretical work mentioned, is quite torsional, but from a certain point of view, the references to Reicha occur systematically. - The rule for the inclusion of such references is, surprisingly, Janáček's evaluation of Reicha's historical significance. Then, in several places of Janáček's theoretical work, we will meet the name of Antonín Reicha, as an important figure and also constituent of the music-theoretical tradition, both in the European and Bohemian context. The evidence for such an investigation is just a little. These are mentions in Janáček's “The Complete Doctrine of Harmony”, mentions in the notes to the lectures "Music Theory and Composition", references to the historical significance of Reicha in a series of five lectures "Composer at work", and the last, most extensive analysis of the Reicha's theory is in the lectures on the topic "Theories of Harmony", which were presented at the Master School of Composition at the Brno Conservatory in the academic year 1919/1920. Another mention, but only illustrative, is in Janáček's correspondence with the Universal edition, concerning the publication of “The Complete Doctrine of Harmony”, where Janáček also mentions Reicha. The paper will focus on the analysis of Janáček's relationship to Anton Reicha. Last but not least, the attention will be paid to the reception of Antonín Reicha's music-theoretical writings in Leoš Janáček's own theory, and we will also add some reflections on the paradigmatic shifts that influenced Janáček's often critical view of the author of the previous epoch.