The contents of kaempherol, quercetin and L-ascorbic acid in sea buckthorn berries were measured at different maturation stages using High Performance Liquid Chromatography (HPLC) methods. The content of ascorbic acid decreased over time with significant differences between sampling dates for the five cultivars studied. The mean decrease was 25% in 19 days, from 1.48 to 1.10 g kg-1. Quercetin decreased whereas kaempherol increased during maturation. Among three studied cultivars, the decrease in quercetin was significant (from 0.028 to 0.014 g kg-1) in 'Otradnaja', where as the increase (from 0.012 to 0.016 g kg-1) in kaempherol was significant in the others two, 'Prozratnaja' and 'Gibrid Pertjik'.;