This article responds to the following research question: if a large number of people experienced in Northern Ireland and the Basque Country the same root causes that increased the likelihood of becoming involved in terrorism, why did so few become terrorists? The article provides an exploratory study of the factors that prevented individuals from joining terrorist organizations in the United Kingdom and Spain, where intense campaigns of violence took place since the late sixties for four decades. The article is based on twenty-seven semi-structured in-depth interviews with men and women who refrained from resorting to terrorism despite sharing similar structural and personal features with those who decided to engage in terrorism. It identifies a combination of inhibitor factors that prevented individuals from following terrorist pathways despite sharing some predisposing risk factors with those who did engage in terrorism as members of organizations like the IRA, the UVF, the UFF and ETA. It also assesses why some types of radicalization developed into violence while others did not as a result of certain barriers.