The results of a series of experiments concerning the GC enantioseparation of some racemates on columns coated with 2,3-di-O-acetyl-6-O-t-butyldimethylsilyl-β-cyclodextrin diluted in two different polysiloxanes (PS-086 and OV-1701) are reported. The investigation is centered on the influence of the diluting phase on the separations of the racemates investigated [δ-heptalactone, linalyl acetate, and an homologous series of cis-2-(2-alkyl-cyclopropyl)-ethanol (alkyl from ethyl to heptyl)] because one of the two polysiloxanes separated them, whereas the other did not. Column retention and efficiency characteristics were investigated as a function of the diluting phase. Retention increase (RI) and Gibbs–Helmholtz parameter (ΔR,SΔG) were determined for each of the above racemates, analyzed by different mixtures of the CDD selector with the two diluting phases. © 1995 John Wiley & Sons, Inc.