This article explores the link between radicalization patterns and modes of attack planning and preparation among lone-actor terrorists. Building on theorized patterns of lone-actor radicalization, we discuss and compare their modes of pre-attack behavior, including target and weapon choice, observance of operational security measures, likeliness of engaging in leakage behavior, and the overall amount of time devoted to these activities. This exploratory study builds upon a dataset of thirty-three lone-actor terrorist cases in North-America and Europe between 1986 and 2015. The analysis suggests that specific patterns of radicalization are linked to systematic differences in modes of attack planning and preparation. The results provide insights into the heterogeneity of terrorist involvement and tentatively suggest the potential importance for law-enforcement agencies in using case-specific knowledge on radicalization patterns to inform forecasts of likely pre-attack behaviors.