Quedius dilatatus is a rove beetle rarely reported from Poland. It is found in parks, on trees along roads, and less often in forests. It develops in the nests of hornets. Q. dilatatus is for the first time reported to occur in the Rogalin Landscape Park (Wielkopolska-Kujawy Lowland), Knyszyn Forest (Podlasie), Miejsce (Lower Silesia), and in a residential building in the Białowieża Forest. Q. dilatatus is an umbrella species which co-occurs with other rare saproxylic beetles, but its synanthropisation has been observed.