The observations carried out in the winter of 2008/2009 reveal invasive species Oxycarenus lavaterae on linden species in the town of Piteşti and for the first time in Romania. The evidence suggests a western route of entering Romania. O. lavaterae overwinters in aggregations containing approximately equal numbers of females and males. Out of 1,254 individuals observed, the males accounted for 50.8%, and the females for 49.2%. The average value of the density of individuals in the collected samples is of 62 specimens/ cm3, so, the size of the aggregations ranges from a few thousand to tens of thousands of individuals. Under the specific conditions of the years 2010 and 2011 in Piteşti, our observations lead us to consider that the species had only one annual generation. The local administrative authorities monitor this species, and insecticide treatments are applied when appropriate.