The present study reports about the plasma carotenoid levels of chickens achieved after feeding diets containing free and esterified lutein (from marigold) and capsanthin (from red pepper) by applying HPLC analyses using a RP-C30 column. Forty chickens were divided at random into four groups and were fed 2 wk with different diets after receiving a basal diet with a low carotenoid content for carotenoid depletion (3 wk). One group was fed a diet containing free lutein (G1), another group received a diet with esterified lutein (G2), two other diets contained free (R1) and esterified capsanthin (R2), respectively. To unequivocally identify plasma carotenoids, liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry analysis was applied, which had never been used as an analytical tool to evaluate the carotenoids of chicken plasma; HPLC chromatograms of chicken plasma following capsanthin feeding have not been presented. The study showed that not only lutein but also capsanthin appeared in the blood stream after feeding free or esterified xanthophylls, demonstrating that capsanthin esters were bioavailable. Quantitative analysis showed comparable concentrations of plasma lutein and capsanthin, respectively, no matter if free or esterified carotenoids were fed.