The quality of the organically produced fruit and vegetables is a frequent subject of research, but very few authors have investigated the differences in the content of biologically active compounds in organic agricultural crops depending on the age of the organic farms. At the same time, many studies have shown that the soil and the whole agroecosystems need time to stabilize after conversion of land to organic production. It suggests that in a mature, stable organic system one could expect higher yields and high quality of the crops. The aim of this study was to verify the following hypotheses: (1) the content of bioactive compounds in agricultural and horticultural crops is higher when they come from the organic production system compared with the conventional crops; (2) the content of bioactive compounds in crops is higher when they come from organic farms applying organic production standards for many years compared to those from the recently converted farms. The research material consisted of potato tubers (Irga variety), carrot roots (Flacoro variety) and apple fruit (varieties Idared and Antonówka) produced in (a) conventional farms, (b) organic farms in the second or third year after conversion, (c) organic farms in the fifth or sixth year after conversion, (d) organic farms over eight years after conversion. The collected fruit and vegetable samples were analyzed for dry matter, vitamin C, polyphenols, phenolic acids, flavonoids, carotenoids and chlorophylls. The results confirm the higher content of bioactive compounds in apples and carrots produced in organic compared to the conventional farms (this applies to most of the tested compounds in apples and total polyphenols & phenolic acids in carrots). At the same time, there was no significant impact of the production system on the content of the tested compounds in potato tubers (with the exception of ferulic acid and rutin, which were found in higher contents in the conventional tubers). In case of potatoes there was also no significant effect of the age of organic farms on the chemical composition of tubers. The exception was again ferulic acid and rutin, which, however, were found in higher contents in tubers from <3-year-old organic farms compared to those converted before 5-6 years. For carrots, the results did not confirm the hypothesis about the effect of time after conversion on the crop quality - the total content of polyphenols was highest in the carrot roots coming from the <3-year-old farms, significantly lower in the 5-6-year-old farms, and the lowest in the oldest (>8-year-old) farms; similar trends were found for phenolic acids and flavonoids (total). For carotenoids, dry matter and vitamin C no statistically significant differences were found between the carrot samples depending on the age of organic farms. In case of apple fruit, only 5-6-year-old and >8-year-old orchards were compared. Similarly to carrots, apple fruit from older (>8-year-old) orchards contained significantly lower contents of many of the tested compounds (flavonoids, carotenoids, chlorophylls) and dry weight compared with fruit from the younger (5-6-year old) orchards. However, the total content of polyphenols in apple fruit did not differ significantly depending on the age of organic farms. In conclusion, the study did not confirm the hypothesis that the content of bioactive compounds in plants is higher when they come from the farms applying organic production standards for many years compared to those just recently converted. In order to assess what other factors (agronomic practices, soil, weather, climate) affected the quality of agricultural products to a greater extent than the period of organic cultivation, the study should be continued on a wider scale.