CEP services (Courier, express and parcel services) are currently showing a strong growth trend. In Germany, for example, more than 2.9 billion CEP shipments were sent in 2015. This figure is expected to increase by 5.1 percent to almost 3.8 billion shipments per year by 2020. In this context, online purchases also play an important role. Current surveys on the European level show that 57 percent of all EU citizens shopped online in 2017, in Germany even 75 percent. Also smaller EU countries like Poland show unambiguous trends in online shopping: While in 2008 online trading only played a minor role (18 percent) in Poland, in 2017, the number of those shopping online increased to 45 percent. With a growing need for CEP services, resource consumption also increases and so does the resulting environmental impact. At the same time, CEP services with their complex chain of transport and logistic elements offer multifaceted potentials to reduce negative environmental effects. This is true for CEP shipments between companies (business-to-business services) as well as individuals and companies.In the project SEEK CO2URIERS, we systematically investigate motives for the willingness to individually compensate for CO2 emissions in a field experiment in cooperation with a courier service provider.