Abstract 1. 1. 13C NMR spectra of twelve alkyl adamantanes were studied and their structures correlated with carbon chemical displacement. It was shown that 13C NMR spectroscopy is a very effective method for investigating alkyl adamantane structures and at the same time enables the type of substitution in the adamantane nucleus to be determined. 2. 2. It was established that the effect of alkyl substituents on chemical displacements of 13C in di- and polyakyl adamantanes is additive. 3. 3. It was found that alkyl and adamantyl radicals have a mutual de-screening effect in the alkyl adamantane system showing a displacement to the weak field of peaks of the α-carbon atom of alkyl and nearest carbon atoms of adamantane nucleus. 4. 4. It was established for 2-alkyl adamantanes that γ-syn-carbon atoms of the adamantane nucleus interact with alkyl substituents: this is shown by the difference of chemical shifts of γ-syn- and γ-anti-carbon atoms of the adamantane nucleus.