Information and Communication Technology (ICT) can have both negative and positive impacts on the environment. Immediate negative environmental impacts arise due to the production, use and disposal of ICT products, while positive effects can arise because ICT products and services replace other products. Other, more indirect consequences of introducing new technologies include e.g. that money saved by reducing costs due to ICT-induced energy efficiency, is being used in consumption of other goods and services that also need energy in their production. Such effects are examined within different disciplines under headings such as rebound effects, indirect effects, second order effects and ripple effects. This paper presents a review and discussion of different second order effects that can be linked to ICT usage in general, using e-commerce as an example. This is a first necessary step in developing methods which include second order effects when analysing the environmental impacts of ICT.