Within the scope of the doctoral dissertation, the influence of light emitted by light emitting diodes on bioactive compounds in fruit and vegetables during storage was examined. Additionally, activities of two enzymes of the phenylpropanoid/flavonoid pathway, namely phenylalanine ammonia lyase (PAL) and flavonoid 3’-hydroxylase were determined. The fruits' responses to irradiation were LEDs wavelength, treatment duration and fruit species and cultivar dependent. In general, the major changes in bioactive compounds were determined in the content of anthocyanins. Blue light at 444 nm significantly increased their accumulation in cherries and apple peel. No changes of other phenolic contents were observed in cherries while in apples chlorogenic acid and three out of six studied quercetin glycosides increased in all cultivars studied. Contrary to natural light conditions, LED irradiation of ‘Idared’ apples at 444 nm did not induce the accumulation of peonidin 3-O-galactoside. High positive correlations between individual anthocyanins and PAL activities were determined in cherries and apples. Moreover, highly significant correlations were found between anthocyanins and colour parameters hue, C* and ΔE. In apples, red light did not significantly affect the contents of anthocyanins, flavonols, and flavanols. Irradiation with LEDs at 420, 444, 620 and 740 nm decreased the chlorophyll a and b contents as well as β-carotene, neoxanthin, and violaxanthin. Zeaxanthin accumulation was induced by a red LED light at 740 nm.