An analytical method based on CZE to determine lansoprazole enantiomers in pharmaceuticals was developed. The primary factors affecting its separation efficiency, which include chiral selector, pH, buffer concentration, capillary temperature and injection time, were optimised. The best results were obtained by using a background electrolyte consisting of 50 mM phosphate adjusted to pH 2.2, 12 mM beta-CD and 5 mM sodium sulphite, in combination with hydrodynamic injection and a 15 kV separation voltage. Detection limits were calculated from baseline noise and found to be 0.64 mg L-1 for the R enantiomer and 0.72 mg L-1 for the S enantiomer. The proposed method was used to analyse three different pharmaceutical preparations with recoveries of 91-102% of the label content.