Isotope depletion (or enrichment) of large biomolecules is a procedure already used in high resolution Fourier transform ion cyclotron resonance mass spectrometry for improving the reliability and accuracy of biomolecular mass characterization. In this work, effects of isotope depletion on a number of mass spectrometric parameters are systematically studied. Implementation of the isotope depletion techniques in conjunction with lower resolution mass analyzers is discussed as well. We investigate theoretically the position of the centroid of the isotopic mass distributions (centroid mass) and the shift between the monoisotopic and the centroid masses of biopolymers as a function of the isotope abundance (e.g., 12C:13C ratio). The behaviour of other additive mass parameters, like the ratio between the monoisotopic and the first isotopic peak, is also discussed. We address by computer simulations the effects of different instrumental parameters like mass resolution and ion statistics as a function of isotope abundances and from there the achievable mass accuracy for high-mass biopolymers. We assess some of the practical issues of the isotope depletion technique, viz., to what degree and with what accuracy the depletion procedure should be performed for achieving the desired mass accuracy.