Meanwhile In the U.S., online ad spend reached €16.6 billion ($23.4 billion) in 2008 and grew by 10.6 percent, suggesting the European market could overtake it in the next couple of years.

Despite the fact markets such as Slovenia and Poland experienced growth rates upwards of 60 percent in '08, the study found that six of the top ten European markets grew by less than 20 percent. These ten markets currently account for 93 percent of total European spend.

Among the most established European markets, Spain showed relatively strong growth at 26 percent, as did Denmark and Norway with 22 percent growth each. France and the Netherlands experienced the weakest growth at 18.5 and 9 percent, respectively.