Protest is a common, if somewhat contested, form of political engagement. Little is known, however, about the decision to participate in illegal protest as a form of civic engagement. Using data from the International Civic and Citizenship Education Study 2009 (ICCS 2009) (Schulz et al. 2010), the current study explored Hong Kong adolescents' intentions to engage in protest activities. Mixture Rasch modelling was chosen for data analysis. Two latent classes with different participation patterns were identified and labelled 'Radicals' and 'Rationals'. Multilevel logistic regression was used to assess key predictors of group membership. Student-level results indicated that citizenship-efficacy, corruption acceptance and the use of connections were the predictors for inclusion in the Radical group. Parents' political interests, good student-teacher relationships, positive attitudes to good citizenship, support for gender equality and traditional cultural values predicted membership of the Rational group. School-level results indicated that in less SES advantaged schools, students' endorsement of illegal protest was higher.