This chapter first examines the situation of terrorism in the present world with the conclusion that without financial support, terrorist warfare and activities could not be sustained for very long. Next, the chapter addresses the 1999 Financing Terrorism Convention. In addition to the commission (provision or collection) of the offences defined in the Convention, Article 2(5) requires the criminalization of other activities, such as attempts, the participation as an accomplice in a defined offence, the organization of such an offence, or direction of others to commit such an offence as well as the intentional contribution to the commission of such an offence by a group acting with a common purpose, under certain defined circumstances. The chapter goes on to conduct a comparative study of the various modes of participation taking into account the jurisprudence of the ICTY, ICTR, ICC and other international/ised criminal tribunals. It is suggested that all the activities listed in Article 2(5) of the Financing Terrorism Convention, except attempt, be regarded as modes of liability rather than inchoate crimes.