Аннотация:We discuss the cyclotron resonance study of doped and undoped InAs/AlSb quantum wells with a two‐dimensional electron gas density ns = 3⋅1011 – 8⋅1012 cm−2. A remarkable increase of the cyclotron mass from 0.03m0 to 0.06m0 with the electron concentration is observed and shown to be a result of the conduction band nonparabolicity.