Inhaler (1) for powder, especially medical substances comprising suction air duct (12) extending to mouthpiece (3), reservoir (11) for substance (10) linearly moveable dosage chamber (26) for separating a specific amount (101) of substance (10) from reservoir (11), which is then transferred to suction air duct (12). Dosage chamber (26) can be rotated in a superimposed fashion while being arranged eccentrically relative to a corresponding inhaler rotation axis (x).