Drawing on recent literature on the environmental impact of information and communication technologies (ICTs) and the Internet, this paper identifies three main types of effects: direct impacts of the production and use of ICTs on the environment (resource use and pollution related to the production of infrastructure and devices, electricity consumption of hardware, electronic waste disposal); indirect impacts related to the effect of ICTs on production processes, products and distribution systems (de-materialisation, substitution of information goods for material goods, and substitution of communication at a distance for travel); and structural/behavioural impacts, mainly through the stimulation of structural change and growth in the economy by ICTs, and through impacts on life styles and value systems. This paper argues that the diffusion and use of ICTs are leading to both positive and negative environmental impacts. However, because the effects of ICTs on economic activity are pervasive, their impacts on the environment are difficult to trace and measure. The paper argues for a need to move beyond the dichotomy between pessimism and optimism demonstrated in much of the emerging literature. Instead the relationship must be recognised as complex, interdependent, deeply uncertain and scale-dependent. © 2004 Elsevier Ltd. All rights reserved.