Abstract In Poland, the share of Diptera in the species composition of the harmful entomofauna occurring on vegetable crops ranges from 20 to 25%. They occur on all vegetables grown in Poland (over 80 species and botanical varieties). Since the systematic registration of pests inhabiting crops in Poland in 1919, over 70 species of flies have been listed as pests of vegetable plants. Species from three families dominate in terms of population and numbers: Anthomyiidae with 12 species (Delia radicum, on early and late cultivars of cruciferous vegetables, mainly broccoli, cauliflower, white cabbage, kohlrabi, and radishes; Delia platura occurs annually on bean and cucumber; Delia antiqua on onion and garlic; and Pegomya hyoscyami on beetroot), Cecidomyiidae with 10 species (two species dominate, Contarinia nasturtii and Dasineura napi, on cruciferous vegetables), and Agromyzidae with 23 species (Liriomyza bryoniae on cucumbers, tomatoes, and peppers, and Phytomyza gymnostoma on leeks). Short-term, gradational occurrence of some dominant species was found, including Botanophila gnava (lettuce), Chamaepsila rosae (carrot, parsley), Delia platura (asparagus, bean), Delia radicum (broccoli, cauliflower, kohlrabi, radishes, white cabbage), Phytomyza gymnostoma (leek), Oscinella frit (corn), and Suillia lurida (garlic). However, they did not affect the level of plant production in the following years of cultivation. Apart from phytophagous species, taxa with a different trophic structure are common. These are copro-, necro-, sapro-, and zoophagous species. The most numerous were flies from the Drosophilidae family (Drosophila busckii, Drosophila limbata, Scaptomyza pallida, Fanniidae (Fannia canicularis, Fannia scalaris), Heleomyzidae (Tephrochlamys tarsalis), and Muscidae (Muscina levida, Muscina stabulans, Phaonia trimaculata). Natural enemies of insects play an important role in vegetable agrocenoses. Species belonging to the order of Coleoptera beetles (Carabidae and Staphylinidae), Syrphidae, Tachinidae, and Muscidae, mainly Phaonia trimaculata larvae, play the most important role in reducing the number of Diptera. In addition, the number of phytophages is limited by other organisms, e.g., Diplopoda, Nematoda, Arachnida, and pathogens of viral, bacterial, and fungal origin.