The effect of substrate pH level (4.7, 3.3 and 7.3) on the anthocyanin, quercetin compounds, catechin and phenolic acids concentrations in petals of Rosa x hybrida L. ‘KORcrisett’ and on the number of flowers per plant was investigated. The phenolic profiles of this plant were established for the first time by the use of HPLC/MS. Plants potted in a substrate with pH 4.7 developed significantly more flowers compared to those planted in an acidic (3.3) and alkaline (7.3) pH levels. However, the concentration of anthocyanins, quercetin compounds, catechin and phenolic acids was always lowest in the petals of ‘KORcrisett’ rose plants potted in pH level 4.7. Compared to the first sampling, a significant increase in the concentration of major and total anthocyanins and quercetin compounds was measured in the petals of plants potted in pH level 3.3 and 7.3, but not in the plants potted in pH level 4.7, respectfully.