The aim of this study was to screen seized illegal cannabis plants for pesticides. Cannabis samples were analysed according to the EN 15662 method. Pesticides were detected with UPLC/MS-MS in positive ESI mode using multiple reaction monitoring and GC-MS using scan mode. A total of 50 samples were tested for 160 different pesticides. Seven different pesticides were detected in 19 samples and five samples contained two pesticides. Four of the pesticides detected were fungicides (propamocarb, tebuconazole, propiconazole and tolylfluanid). The other 3 pesticides detected were insecticides or acaricides (imidacloprid, bifenthrin, and hexythiazox).