Information and communication technology (ICT) provides unprecedented opportunities to reduce greenhouse gas (GHG) emissions from passenger transport by avoiding, shifting or improving transport. Research on climate protection through ICT applications in passenger transport mainly focuses on theoretical potentials, is assuming that digitalmobility services replace GHG-intensive transport modes (e.g. car travel), and does not specify the conditions under which decarbonization potentials will materialize. It is known that digitalmobility services can also take a complementary (as opposed to substituting) role in travel or replace non-motorized travel, which can increase GHG emissions. Based on existing literature, we develop a conceptual framework to guide qualitative and quantitative assessments of the relationship between ICT use, passenger transport and GHG emissions. The framework distinguishes three types of effects: (1) First-order effects, GHG impacts of producing, operating and disposing the ICT hardware and software, (2) second-order effects, impacts of ICT on properties of transport modes, transport mode choice and travel demand, and (3) third-order effects, long-term structural changes due to ICT use (e.g. residential relocation). We qualitatively demonstrate the framework at the example of automated driving and discussmethodological challenges in assessments of ICT impacts on passenger transport such as the definition of system boundaries, consideration of socio-demographic characteristics of individuals and the inference of causality. The framework supports researchers in scoping assessments, designing suitable assessment methods and correctly interpreting the results, which is essential to put digitalization in passenger transport at the service of climate protection.