Invasive species are alien elements of flora and fauna to our environment, in each case their occurrence is a very serious threat to native organisms. Invasive insects damage trees of great significance in park sites. They face very little resistance from the environment and substantially affect the decorative character of plants. A well-known representative of the group of phytophages is Cameraria ohridella or Horse-chestnut leaf miner occurring on horse-chestnut. Recently, Phyllonorycter issikii was observed on lime trees, P. robiniella on Black Locust and P. platani on plane trees in the historical parks of the city of Rzeszów and its surrounding. Newly identified in Rzeszow and potentially dangerous pest of plane trees is also Corythucha ciliata, an insect in the Coreidae family. Another risk for trees and shrubs may be the Western conifer seed bug Leptoglossus occidentalis, which is more and more frequently observed in different parts of Rzeszów.