Phenolic compounds of Thymus praecox Opiz subsp. caucasicus var. caucasicus were analyzed by high performance liquid chromatography equipped with an ultraviolet detector (HPLC-UV). Quercetin (co-eluting with luteolin) and caffeic acid were among the most abundant compounds identified. In addition syringic, ferulic, p-coumaric, protocatechuic,p-hydroxybenzoic and vanillic acid as well as the flavonoids catechin, epicatechin, and kaempferol were identified and quantified in the plant extracts. Acidic hydrolysis was used to gain additional information on the glycosylation state of the phenolics. Although chromatographic profiles changed considerable upon hydrolysis, quercetin and caffeic acid remained among the most abundant compounds identified. In addition the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activities of different tissues were determined and correlations were found between phenolic or flavonoid content and antioxidant property with strongest radical scavenging activity in hydrolyzed flower extracts. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.