The results of the study on the content of selected chemical components of watermelon (total sugars, reducing sugars, vitamin C, carotenoids and beta-carotene) of Polish cultivar ‘Bingo’ are presented in the paper. Cultivation was conducted in two successive vegetative seasons (2005 and 2006) near Bydgoszcz, with the use of drip irrigation. During seedling production three different variants of irradiation were used: sunny light, artificial daylight and artificial blue light. The drip irrigation, used during the vegetative season, decreased the content of total sugars as well as that of carotenoids and beta-carotene in watermelon fruits, whereas the content of reducing sugars and vitamin C was higher than that in fruits obtained from control plots (without irrigation). Irradiation with artificial daylight during seedling production had a positive influence on the content of total carotenoids, beta-carotene and vitamin C in watermelon fruits. The content of sugars was differentiated in fruits of watermelon by irradiation of seedlings. Fruits of plants originated from seedlings irradiated with sunny light were characterised by the highest content of sugars.