Aedes albopictus (Skuse) was detected for the first time in Italy in 1990. Thanks to its high biological adaptability, it spread rapidly to colonize various urban areas in central and northern Italy. The purpose of this study was to examine the ecological niche occupied by Ae. albopictus and the role of competition with Culex pipiens L., which is a widespread indigenous species, in urban areas. The larval development cycle and competition for food between the two species was also studied under laboratory conditions. The study showed that both species can colonize any type of artificial water container. Ae. albopictus mainly occupies saucers under flower pots and other, usually smaller-sized, containers, whereas Cx. pipiens tends to develop more in large tanks (100–200 liters) used in residential gardens and other larger-sized containers. It would seem that the two species interact mainly in medium-sized containers (10–50 liters) such as manholes and tires. Laboratory studies showed that, at 25°C, the food-biomass conversion coefficient is significantly higher in Ae. albopictus than in Cx. pipiens, indicating that the new established species is more efficient in transforming food into biomass. As a consequence, it has a greater capacity to exploit food resources and therefore grow more rapidly than Cx. pipiens. In larval association where food was scarce, it was noted that competition between the two species takes place and is influenced by temperature: at 25 ± 2°C, Ae. albopictus prevails but is much less likely to do so at 20°C.