Exptl. studies of microdosimetry in therapeutic ion beams have been performed using several detectors. The differences among the microdosimeters lie on the shapes, the site sizes, and the material. Coin-shaped solid-state detectors made of silicon or diamond with thickness varying from 0.3 μm to 10 μm, as well as proportional counters with spherical and cylindrical sensitive volumes filled with tissue-equivalent gas are the microdosimeters used in therapeutic proton and carbon-ion beams. One goal of microdosimetry in the clin. environment is providing a reliable and repeatable specification of the radiation quality of the radiation field. A methodol. should be developed to provide, independently from the heterogeneous information collected with the different detectors, a detector-independent specification of the radiation quality. Historically the specification of the radiation quality is provided either, in terms of Linear Energy Transfer (LET) or in terms of lineal energy, y. The first part of this study focuses on identifying the correlation between the distributions of LET and the lineal energy spectra as well as the correspondence between their mean values calculated in frequency and in dose. The evaluation is based on the method of LET anal. described by Kellerer making the necessary adaptation to the peculiarities of the ion-beam therapy where the pristine irradiation is unidirectional and made of a single species of ion essentially mono-energetic. The second objective of this study is to interpret the spectra collected by a slab and perform the necessary conversion to estimate what the spectrum would be if it was collected by a detector different in shape, material, or size. An example is provided to confirm the methodol. starting from the simulated lineal energy spectrum obtained for carbon ions in a slab detector of graphite and converting it to the spectra that would be obtained in the same radiation field for spherical, cylindrical, and slab detector made of water.