The distributions of the tetraploid Anthoxanthum odoratum and diploid A. alpinum were first studied in the Krkonoše Mts (part of the Sudetes Mts) to find the transition zone where both species occur together and then their ecological requirements in this zone were determined. The distribution was studied at two spatial scales, geographic and local; the latter included detailed distribution at a locality level, where the relationships of both species to plant communities were investigated. The zone where the overlap occurs is between 800–1290 m a.s.l. Anthoxanthum alpinum is able to descend to even lower altitudes, where it grows in vegetation dominaned by Nardus stricta. The species commonly occur in a fine mosaic of plant communities of Polygono-Trisetion (A. odoratum), Nardion (A. alpinum) or Nardo-Agrostion tenuis (both species). Anthoxanthum alpinum also occurs in areas that are currently not in direct contact with either alpine or subalpine vegetation (the Rýchory ridge, Černá hora Mt).