In 1993–1997, 990 pupae of diamondback moth (Plutella xylostella L.) were collected from nine different varieties of Brasica oleracea L., grown on experimental farm near Kraków. Only 234 moths (23.6%) were recovered from the cocoons. The most important factor reducing the population of DBM was parasitization (65.1%). It varied between the years of observation and oscillated from 60% to 90.3%. Sixhundred and fourty four specimens of parasitic wasps belonging to 11 species from families: Ichneumonidae (5 species), Braconidae (3 species), Pteromalidae (2 species) and Eulophidae (1 species) were reared out. In each year of observations the most abundant species among DBM parasitoids was Diadegma fenestralis Holmgr. as it constituted 71.4% of all of the wasps reared. In the years 1994 and 1996 with low abundance of diamondback moth, D. fenestralis was the only species parasitizing 66.7% and 89.5% of the pest larvae.