Criminological research usually directs its focus at traditional forms of offending. The purpose of this article is to discuss the extent to which traditional criminological theories can be used to understand a modern form of terrorism. The main issue to explain is why young men and women from a Western European country, such as Sweden, are joining Daesh in Iraq and Syria. The conclusion is that many criminology theories are useful to analyse the factors behind the affiliation to Daesh. The majority of those recruited into this organization have in many respects a similar background to individuals recruited to other forms of serious organized violent crimes. It should be noted that many of the theories discussed in the paper are more relevant for the understanding of why men join Daesh. When it comes to the recruitment of women these theories’ explanatory value is more limited. However, this applies also to these theories’ ability to explain female crime in general.