A burgeoning international interest in Carbon Capture and Storage (CCS) as a means of mitigating the effects of climate change has raised a number of novel legal issues, one of which concerns ownership of the underground sites in which captured carbon dioxide can be stored. This paper considers the extent of a surface landowner's rights above and below land and explores the treatment of underground space within the context of CCS in relation to differing jurisdictions. Particular attention is paid to legal principles applied in the United Kingdom and the United States, and consideration is also given to relevant legislation in Australia and Canada.