CO2 injection into tertiary oil reservoirs has been widely accepted as an effective technique for enhanced oil recovery (EOR), and has been used by the oil industry for over 40 years. Concerns over greenhouse gas emissions are leading to the investigation and realisation of its potential as a carbon storage method in recent years. With the right reservoir conditions, injection of CO2 into oil reservoirs can result in incremental oil recovery and permanent storage of CO2 in geological formation. The majority of previous and current CO2 EOR projects use l ow cost CO2 sources and have good economic returns in terms of high gas utilisation efficiencies (167-227 sm3 CO2/STB oil). The potential of CO2 storage combining EOR is high; approximately 60% injected CO2 can be retained in the reservoir at the CO2 breakthrough if reinjection is not considered. It has been accepted that there is little major technical challenges for CO2 EOR projects, but there are economic constrictions if high cost anthropogenic CO2 (such as from power plant) is used for EOR and storage operations. In this chapter, a general revi ew is given on the CO2 EOR and storage potentials, field screening and economic analysis. A case study for CO2 EOR application in a North Sea field is also presented. Copyright © 2005, Institut français du pétrole.