Unequivocable evidence for warming of the climate system is a reality. An important factor for reducing this warming is mitigation of anthropogenic CO2 in the atmosphere. This requires us to engineer technologies for capture of our carbon emissions and identify reservoirs for storing these captured emissions. This chapter reviews advances made in understanding multiphase interactions and processes operating in a variety of subsurface reservoirs using noble gases. We begin by discussing the types of reservoir available for carbon storage and the mechanisms of viable CO2 storage, before summarising the physical chemistry involved in data interpretation and the sampling/sample storage techniques and requirements critical to successful sample collection. Theory of noble gas partitioning is interspersed with examples from a variety reservoirs to aid our knowledge of long term CO2 storage in the subsurface. These include hydrocarbon reservoir and natural CO2 reservoirs. In these examples we show how good progress has been made in using noble gases to explain the fate of CO2 in the subsurface, to quantify the extent of groundwater interaction and to understand CO2 behaviour after injection into oil fields for enhanced oil recovery. We also present recent work using noble gases for monitoring of subsurface CO2 migration and leakage in CO2 rich soils, CO2 rich springs and groundwaters. Noble gases are chemically inert, persistent and environ-mentally safe and they have the potential to be extremely useful in tracing migration of CO2. It is imperative that the many upcoming pilot CO2 injection studies continue to investigate the behaviour of noble gases in the subsurface and develop suitable noble gas monitoring strategies.