Abstract: With the use of the products of free-radical chlorination of indane as an example (data for tetralin are mentioned for comparison), it was shown that only their molecular formulas can be determined as a result of gas chromatography–mass spectrometry analysis, and the reaction mechanism was detailed on this basis. The structure refinement of the components requires an interpretation of their gas-chromatographic retention indices in the form of local additive schemes created for solving a specific problem under consideration. These schemes are sufficiently reliable if they are formed on the basis of data for objects containing all the structural elements of the molecules of characterized compounds. If this condition is not met (as in the case under consideration), the possibility of interpreting retention indices is fundamentally preserved; however, the accuracy of their estimates is significantly reduced and the volume of preliminary calculations increases considerably. The key fragment of the structure of chlorinated indane derivatives, which was almost not represented among the compounds characterized to date, is the chlorine atom in the alicyclic structural fragment in the α-position to the aromatic system. Secondary chlorine derivatives are formed as a result of dehydrochlorination of the primary reaction products with the subsequent addition of chlorine at the C=C double bonds.