A Method and an apparatus for measuring the mass and/or moisture of the contents of incompletely filled capsules, containing, in particular, medicinal products, pharmaceutical products, vitamins and similar products, with the aid of microwaves is disclosed. The displacement of the resonant frequency and broadening of the resonance curve caused by the capsules in at least one resonator is determined and evaluated. Measurements are made integrated over the whole capsule as well as with high local resolution for various portions and cross sections of the capsule.