Various studies have assessed the GHG footprint of the ICT sector (ICT end-user devices, data centers, telecommunication networks) and the potential of ICT use cases (e.g. smart homes, ride sharing) to avoid GHG emissions in other sectors (e.g buildings, transport). We systematically compare relevant studies from the last ten years and discuss the robustness of results in view of the methods used. The results show that the ICT sector causes between 1.5% and 4% of global GHG emissions, a major share of which is due to the production of ICT end-user devices. Estimating GHG impacts of device production is the main source of uncertainty. Results of studies on ICT's GHG abatement potential are less robust, in particular due to uncertainty with regard to use case impacts in a real-life setting, types and sizes of economy-wide rebound effects. Thus the existing studies do not provide a reliable basis for estimating the actually realized GHG abatements. To improve the assessment results and provide a more reliable basis for deriving GHG reduction measures future research should empirically investigate which solution design and accompanying policies are suitable to exploit GHG reduction potentials in real-life. Results of these studies would also increase the robustness of assessments of GHG abatement potentials.