<p>Based on a series of studies recently carried out at the Crimean Astrophysical Observatory, we have analyzed the chemical composition of 20 G- and K-type giants with magnetic fields, comparing them with the chemical composition of 7 non-magnetic giants. Significant differences have been found in the lithium abundance and in the [N/C] ratio between magnetic and non-magnetic giants; both of these parameters are known to be sensitive indicators of stellar evolution. Lithium is shown to be absent in almost all non-magnetic giants, in full agreement with theoretical predictions concerning the evolution of giants that have undergone deep convective mixing during the first dredge-up. In contrast, most magnetic giants retain detectable lithium in their atmospheres. Furthermore, the [N/C] ratio, examined as a function of stellar age and mass, displays systematic differences between magnetic and non-magnetic giants. Possible explanations for the observed differences in the chemical composition of these two types of giants are discussed. It is also shown that the total C+N+O abundance, which apparently remains constant throughout the evolution, exhibits a clear dependence on [Fe/H] not only for the giants analyzed here, but also across a wider range of metallicity from –2.5 to +0.3.</p>